Excel spreadsheet being opened in preview mode by some machines

Question

I would really appreciate it if someone could help with a problem that is confusing me.
I am developing an Excel spreadsheet containing a number of macros that are actioned mainly through the use of an ADD-INS customised menu.
The spreadsheet has been deployed across about twenty systems running a mixture of mainly windows 7 64 bit machines with Office 2010 or 2013 installed.
For several weeks each spreadsheet has been updated periodically as new functionality has been added. This has not been a problem until now.
Some, but not all, when they try and open the new version of the spreadsheet get an error 'Application-defined or object-defined error' a number of machines experienced this same problem all at the same time, but not all.
I have ruled out it being an Office version number problem because in both 2010 and 2013, some work some don't.
I can reproduce the exact same problem on the machines that don't have the problem by opening the spreadsheet in preview mode.
I can find nothing that is forcing the problem machines to open the spreadsheet in preview mode and the difference between the previous version of the spreadsheet and the latest version are relatively minor, but the previous version works and the latest version
causes some machines to throw an error.
The section of code that is being highlighted is checking the sheet protection, I have isolated the code and inserted it into a test excel file and it works fine on the machines that are experiencing the problem, so it doesn't seem to be a coding problem.
I feel that I have effectively ruled out any problem with the code itself and so instead concentrated on it being a "preview" mode problem.
I found that if I opened the new version up on the problem machine and applied a self digital certificate to the VBA code and saved it locally then I could get the problem machine to open the new version without an error.
I can't see any need for doing this though, there is no digital certificate on the original spreadsheet and when I isolated the highlighted code I was able to create a spreadsheet on the same development machine and send it over to a 'problem' machine and that
spreadsheet opened and ran just fine.
I am therefore now very confused. This latest version of the spreadsheet is being opened by let's say 50% of the machines in what appears to be preview mode. The machines are all part of the same network and I have checked that they all have the latest Windows
updates applied and all have the same Excel options settings.  
I have checked the security levels and all the machines seem to be set up the same.
I have doubled checked and there is no digital certificate on the original spreadsheet.
I need it to work the way it did before, i.e. each computer receives a new version and can open it without any messing around.
The new version is copied from a networked folder so I have been able to rule out any Outlook security messages to do with email attachments.
Can anyone shed any light as to what could be going on? 
Why are some machines opening this particular spreadsheet up differently to every other spreadsheet?
As it suddenly happened across multiple machines at the same time I was looking at possible Windows updates causing the problem but I have applied all the window updates to two machines and one works and the other doesn't.
I'm running out of ideas.

Answer 1

Hi Jeffrey
>> Excel spreadsheet being opened in preview mode by some machines
>>>Is it caused by the custom code, could you reproduce this issue without the custom code?
I can't seem to isolate the code to cause the problem, when I isolate the code it works.
>> New version of the spreadsheet get an error 'Application-defined or object-defined error' a number of machines experienced this same problem all at the same time
I>>>’m not sure whether it was caused by Microsoft Security Bulletin MS14-082.
>>>Here is a KB for your reference: KB3025036
I have had this problem but managed to resolve that by deleting the .exd files.
>> However it is still a problem for the first machine that experienced the problem, even though the Windows Updates are wholly up to date.
>>>Currently, I’m not able to identify the root cause of this issue, but if this issue could only be reproduced on a specific machine, I will suspect this issue is related to a specific environment. If this is an urgent issue, I will recommend you
creating a support incident so that the engineers could work closely with you to troubleshoot this issue in a deep level, if the support engineer determines that the issue is the result of a bug the service request will be a no-charge case and you won't be
charged.
I have now installed the same spreadsheet on 20 machines.  
15 - installed without any problem,
3 - experienced the problem but then mysteriously worked a few days later without me doing anything other than trying again.
1 - worked only after I digitally certified the VBA on the local machine,
1  - I can't get it to work at all no matter what I do. (Edit the VBA locally, digitally certify the code etc)
I have another 4 machines that need to be done.
For the 1 that I can not get to work at all I have checked that all the windows Updates have been applied. It is a relatively new desktop PC running Windows 7 64 bit and Office 2013.
Does any of that suggest a possible cause? To me it almost suggest a windows update is resolving the problem but if it is it is proving difficult to pin down as to which one.
Martin