Word 2007: Error when saving file that contains equations

Question

Using Microsoft Word 2007, version 12.0.6425.1000 with Service Pack 2
I am a High School Math teacher, and when working on a document that contains a number of math equations. When I try to save the document, Word refuses to save. It displays the following error: "A file error has occurred. <filename>. OK",
and I am unable to save the file. 
Reading the forum, I have found this to be a very common issue going back to 2009, but I have not seen a definitive solution or patch. 
I have found a workaround:
Creat a new document
Copy and paste from the corrupted doc each page, saving the new document after each page
Until I hit the error, then I know the page that has the issue, and can usually narrow it down to a specific math equation. Nothing fancy just some basic math. 
Manually rewrite the equation in the new document and it will successfully save.
But the issue has been occurring more and more frequently now and it is becoming very frustrating. Any help would be greatly appreciated! 

Answer 1

There has been a long time known issue with the equation editor.  it causes document corruption by "losing" XML tags.
Apparently fixes for some causes of these problems have been rolled out in Windows updates. But the problem still exists.  You've got it easy. A lot of people running into this problem are students working on documents, like a thesis, that is on a short
deadline ...
One identified cause of these problems is editing equations
after you created them.  DON'T DO THAT! 
If you have to change an existing equation, create a new correct one and delete the old one.
Simpler fix. Don't use Word (or Office) for creating equations.  Find some other product, like a pencil.
Over in the "Answers" forum there are a couple volunteers, Tony Jollans and Jeeped
, who have been manually fixing this type of error if you post a new question or add a reply to one of the ongoing discussions on this issue.
Sorry.
If you want to invest the time to figure out what your error looks like you may be able to come up with a fix other than copy /paste method.
Can't open Word File because of end tag/start tag mismatch error... XML Tag 
- XML Error – Fix It tool - “The name in the end tag of the element must match the element type in the start tag”
This error is caused when Word either “forgets” to write an XML tag, or writes them in the wrong order.
Tony Jolans was the first person that I heard of with home made tool to fix the problem. Now MS has released a Fix It for one specific variation of the problem.
If the tools don’t fix your problem, the file will have to be fixed manually, repairing the tag order.
The Fix It article notes that the document is still in a fragile state. You have to do some addition fixing to avoid repeats of the problem.
https://blogs.technet.com/b/wordonenotesupport/archive/2011/03/24/error-when-opening-a-word-2007-or-2010-document.aspx
http://support.microsoft.com/kb/2528942- FIX IT
This fix it will work for one specific tag error where there are equations and graphics in the same paragraph AND Office 2010 SP1 has not been applied.
Preventative suggestions
<snip Jeeped>
I don't think that anyone can completely stop editing equations, but pre-planning them should avoid unnecessary edits.
While I have no concrete, reproducible evidence that editing equations is a cause, I have made these empirical observations:
I cannot state precisely what many of the DOCX XML tags do, but basic XML syntax rules would suggest that code like:                   <m:oMath><m:e><m:ctrlPr/></m:e></m:oMath>
... does nothing at all since it closes everything it opens and offers no content. It looks to me that this is a result of deleting one or more characters from an equation.
While Word 2010 reports these as a problem at:                  Line: 2  Column: 0 ... Word 2007 will still report the actual position, e.g.:                
 Line: 2  Column: 2726981 I keep a copy of Word 2007 side-by-side Word 2010 for no other purpose. It's the only Office 2007 program on my computer. This seems like it is actually a step backwards from a resolution since Word 2010 no longer seems
to be able to parse its own error.
Whether the syntax is truly useless and non-effective for any intent or purpose is actually beside the point. The syntax passes conformity tests and the DOCX
should launch. Why an 85 page document is 'broken' due to a few empty XML formatting tags while retaining legal syntax structure is beyond me.
I try to pass along the area that the problem was in and several times people have remarked that the area I report was the place they were last making modifications/deletions to equations (not additions) when the no-load corruption
occurred.
When no indication from the OP is offered on what was worked on last, the Line: 2 Column: 0 corruption often comes within a formula at the very end of the unfinished Word/Document.xml file and it may be inferred
that this was the last place being worked upon.
The corrupt DOCX files I've worked on are very commonly at the last stages of development with a large complex document. While there couldn't be a worse time for a corruption to appear, it would seem that small edits to existing content are causing
it and not large scale new content generation.
Not one of these points is a definitive 'smoking gun', but put together they seem to indicate
formula editing and not formula writing as a cause for the Line: 2 Column: 0 corruption. If it looks like a duck and quacks like a duck, it is most often a duck.
</snip>
Copy “True Autosave Macros for Office” to this place in reply
Let me fix it myself
If you are familiar with editing XML, you can try to fix the problem yourself by correcting the sequence of the mismatched oMath tags in the document. See the following example:
Incorrect tags:
<mc:AlternateContent>
<mc:Choice Requires=”wps”>
<m:oMath>
</mc:AlternateContent>
</m:oMath>
Correct tags:
<m:oMath>
<mc:AlternateContent>
<mc:Choice Requires=”wps”>
</mc:AlternateContent>
</m:oMath>
Note: You will have to use an application such as Notepad to edit the XML.
Manual Technique
<snip>  A DOCX document is actually a .ZIP file that contains many internal components. There is an internal folder called word which will always contain a document.xml file. This file is the basis of the document's layout
and content.
Assuming that the DOCX archive structure has not been corrupted, it can be opened in an archive utility. I use
WinRAR for this. Once opened in
WinRAR, you can drill down into the
word folder and see the document.xml file. I use
Notepad++ as a text editing tool and have the .xml file extension associated with this program so i can simply double-click
document.xml in WinRAR to open an editing session.
Notepad++ has cursor positioning in the right-hand side of the status bar and finding the position of the error (supplied by a failed open in Word) is pretty straightforward. I look for empty formatting
tags first and only remove content if removing empty tags does not allow the document to be opened. I try to note existing content in the area that I make modifications in order that I can supply position reference information to the owner of the DOCX.
When editing, I assume the philosophy that kess is more. My target is to get the document to open in Word with as little modification as possible and let the original owner of the DOCX make any necessary adjustments.
I should mention that after making a change to word/document.xml you need to save it in
Notepad++ then go to
WinRAR and acknowledge that you want to update the file in the DOCX archive. Once the archive is updated, you can attempt to open the DOCX in Word to see if your efforts are successful.
WinRAR                    
Notepad++                 
</snip>
Further Fixes
The Fix it solution in this article should let you recover your Word document. However, the symptoms will reappear when you make any further edits to the document unless the core problem in the structure of the document is resolved.
To try to correct the core problem, follow one of these workarounds:
Install Office 2010 Service Pack 1
Office 2010 Service Pack 1 resolves this issue for new files. It will also prevent the problem from recurring with any files that were recovered with the Fix it solution in this article.
To download Office 2010 Service Pack 1, follow the steps provided in this Microsoft knowledge base article:
2460049 - Description of Office 2010 SP1
Grouping Objects
The steps provided work best under Word 2010:
After you open the recovered document, turn on the Selection pane. This can be found in the
Home tab of the ribbon. The editing group of the
Home tab has a dropdown button named Select.
Click the Select button, and then click
Selection Pane...
Press the Ctrl button on your keyboard and then click each text box in the selection pane.
Click the Group button under the Format tab. This will group all the objects together.
As soon as you have all objects grouped on each page, save the document under a new name.
Save the document in the .RTF file format
The steps provided work for both Word 2007 and Word 2010:
After you open the recovered document, click File and select
Save (for Word 2007 click the Office button and select
Save As)
In the Save As dialog box, click "Save as type:" dropdown and select
Rich Text format (*.rtf).
Click Save.
Click to view this
blog for more information about this issue.
Bonus tip: Win7 Win8 Math Equation Input Panel / Math input Panel
http://www.lytebyte.com/2009/07/24/guide-to-math-input-panel-in-windows-7/
http://www.7tutorials.com/windows-7s-tablet-input-panel-text-entry-and-handwriting-recognition
http://www.7tutorials.com/training-tablet-input-panel-work-even-better
http://www.7tutorials.com/do-math-easy-way-math-input-panel
Not an answer to the problem, just a bonus that may make it easier to input formula’s in Win7.
Here’s another one of those didn’t-know-it-existed-until-I-clicked-it-by-accident tools in Win7. It’s called the
Math Input Panel.
To access it, simply click Start, and in the Search Box that appears above, type in
Math Input Panel.
The Window should look like this:
Let the fine folks at Microsoft explain what it’s used for:
“Math Input Panel uses the math recognizer that’s built into Win7 to recognize handwritten math expressions. You can then insert the recognized math into a word-processing or computational program. “
Tony Jolan’s Automatic Fix
Download  http://www.wordarticles.com/temp/Rebuilder.dotm Microsoft Office Word Macro-Enabled Template (.dotm) and open it.
Click Options button on the Security warning and select Enable this content.       
Click the Broken Documents tab at the far right of the ribbon.      
Click the Rebuild button in the left-hand side      
Locate and open your corrupt document in the file open dialog.
That's it. The process will repair your document if possible and create a new document with (Rebuilt)
appended to the filename. Be patient as it may take a few minutes. If a repair is not possible, you can then post to a public file area and someone here can attempt a manual repair.
Manual Fix
XML Maker V1.1 is free. It will allow you to open the document.xml file and edit it. It also marks errors and warnings. 
I just didn’t have much luck working with it.
A poster used XML Maker V2.1 (US$125, 30day free trial, enough for average person to fix a file)
Notepad ++ is a good, free editor for this type of task
Make a copy of the file
Rename the copy from DOCX to ZIP
Open … .ZIP/word/document.xml in notepad
Copy the contents of the file to clipboard
Open Word
Paste a copy of the copied XML into Word
(optional) the XML is one long string too hard to read, you can replace some tags, with that tag plus a para mark to break up the text to make it more people readable.
Open an XML validator, ie this site on the internet:
http://www.w3schools.com/xml/xml_validator.asp
Paste another copy of the XML into the “Syntax Check Your XML” input window
Click on “validate” button
Copy the missing tag, ie </mc:Fallback>  (yours will be different)
Return to word Find: mc:Fallback>  (without the </ so you find both open and closing tags). 
Repeat find until you hit 2 open tags in a row.  Then you just have to figure out where to put the closing tag between them. 
Look for other tags before and after a proper closing tag so you can match the problem area to a good area.
Discussion by many affected people, a couple in discussions are also fixing problem if Tony’s fix doesn’t work
http://social.answers.microsoft.com/Forums/en-US/wordcreate/thread/581159d0-9ebc-4522-b30c-53e33e8268e1
Document Recovery
http://www.wordarticles.com/Shorts/Corruption/Formats.php
This page has the most readable description of Word file structures, DOC and DOCX, I have seen so far
The logical structure of a Word 97‑2003 format document is one of a series of elements arranged in a hierarchy, much like a mini file system. As an example, here is the structure of a simple Word 97‑2003 (.doc) format document:
MyDocument.doc
1Table
*CompObj
Word Document
*SummaryInformation
*DocumentSummaryInformation
The physical structure of the complete file bears little relation to the logical structure; it is, again, of a proprietary design, a compound, or structured storage, file. Briefly, and loosely, the separate logical elements of the file are broken up into
blocks; these blocks are treated as individual units, which units are then organised without regard for their logical arrangement, and catalogued, catalogue and organisation detail being held alongside the blocks themselves, to enable recombination into logical
components when necessary.
Just to give you a flavour, here are some views of three small parts of such a document, viewed in a hex editor:
Views of a Word 97-2003 format Document
The logical structure of a Word 2007 format document is one of a series of elements arranged in a hierarchy, much like a mini file system. As an example, here is the structure of a simple Word 2007 (.docx) format:
MyDocument.docx
_rels
rels
docProps
app.xml
core.xml
word
_rels
document.xml.rels
theme
theme1.xml
document.xml
settings.xml
fontTable.xml
webSettings.xml
styles.xml
[Content_Types].xml
As briefly as before, the [Content_Types] file and the _rels folders, along with the subordinate files therein, contain information about the logical structure, and the two files in the docProps folder contain much the same as the two Information files
in the old format. The document.xml element within the word folder holds the bulk of the document content and the other files within that same folder hold formatting details.
So, you might say, the internal structure of a document has changed a little, so what? There are, however, other changes that make a bigger difference. The first is that, although both logical formats are conceptually similar, they are wrapped up in
completely different ways to make a single file. Instead of the proprietary physical structure used for Word 97‑2003 format documents, a fairly standard, and open, Zip Archive format is used for Word 2007 format documents. The second change is that instead
of using obscure binary codes, everything in Word 2007 format documents, well almost everything, is held in XML format.
All data held as XML? In a standard Zip Package? It should be much easier to work with, then? Judge for yourself; here are some views of parts of a Word 2007 format document taken from a hex editor:
Views of a Word 2007 format Document
FreeFileViewer – reads 100+ text, Office, audio, video format file types – Can open some XML tag error files
http://www.freefileviewer.com/formats.html
Can't open Word file due to undeclared prefix, Location: Part: /word/document.xml, Line:91, Column: 49921
The most likely cause of your particular problem is that you are missing a
schema prefix reference within the opening <document ...> XML tag (usually the second one). Different
schema references are required for various types of specialty content. Here is a sample opening <document ...> tag with a large number of various schema prefix codes. If I remove one or two of these, i can reproduce
your error message.
<w:document xmlns:ve="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"
xmlns:v="urn:schemas-microsoft-com:vml" xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing" xmlns:w10="urn:schemas-microsoft-com:office:word" xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main" xmlns:wne="http://schemas.microsoft.com/office/word/2006/wordml">
It's impossible to blindly say exactly what you are missing but if you post an unadulterated copy of your document to a public file area (as noted above) and post the location back here, someone may be able to help. If you are going to go this route, send
a copy that has not already been subjected to repair attempts.
FWIW, while it may be hard to determine exactly which schema you may be missing, I do not believe that having extras causes any problems.
BTW, you don't actually have to rename the DOCX file extension if you have an archiving program. I use WinRAR and simply
<right-click>, Open With... to expose the archive.