Read/Write errors with FileVault-protected folders

Question

Hi-
New to Mac OS, etc. I have been using the new MacBook Pro for about six weeks, and have now encountered my third show-stopper with a FileVault protected user profile. Each time has basically required a from-scratch removal and replacement of the user account. Now I can't ignore it, since I can't go through this again. Before you tell me (as so many websites do) to drop FileVault, I can't. I'm under a government mandate to encrypt "all user data." I'm open to other approaches, but this should "Just Work," no?
Over time, I start seeing various hiccups in accessing files. These seem to present as longer and longer beachballing inside applications which access the disk (oddly, Firefox seems to be the one most commonly affected; then Mail.app seems to have problems either with file locking, or with bits of one email showing up in another, or much more random lockups with beachballs...)
I have no idea how to troubleshoot... nothing obvious shows up in logs or console (ask me if you know of something in particular to look for.)
This time, I decided to copy the contents of the sparse disk image off to a backup before trying to disable FileVault, since that failed completely last time resulting in significant loss of data (mostly emails that had not yet been backed up). I can now reproduce a problem predictably ... looking for help. In trying to copy the entire contents of my user profile, I get about a few hundred megs (into an 18 GB sparse disk) and bump into a file copy error. It happens in the same file every time. I get a dialog in finder that says "The Finder cannot complete the operation because some data in "xxx.mp3" could not be read or written. (Error code -36)" xxx.mp3 is obviously a real file name, I've elided here.
Now, I try to copy the same file from the terminal using cp, to copy to some stable place like the root of the current (administrator) user's directory. In this case, the system goes somewhat nonresponsive -- big pause at the command line, other applications beachball, mouse works fine, but some parts of other applications non-responsive. Ctrl-C seems to work, after a time, and things go back to normal. "cat xxx.mp3" has the same response.
I have run the Disk Utilities over the sparse image in question, and they report nothing wrong or nothing to fix.
Help! The only comment I find on the support forums for error -36 has to do with SMB, not in the picture here.
JA

Answer 1

As I stated earlier, "The -36 is an i/o error. This means either the file, the directory or the data sectors are damaged."
This message can be generated at the source end or at the destination end when you are copying a file.
The copy process can give the same message if it has trouble reading a damaged sector at the read location or when it tries to write a file to damaged sectors at the destination location.
You have told me that disk utility is telling you that the source directory and data sectors are fine.
Verify disk is not perfect. There are literally hundreds millions of sectors on a drive and it would take hours to check each sector so verify disk is usually an adequate scan but not infallible.
You say you have isolated the issue to corrupt files.
You are blaming the file corruption on file vault when that is not necessarily true.
That is why I had asked you to try to make a copy of the Mail folder to the desktop.
The internal drive is verified.
If you had trouble with that copy I was going to go with data corruption.
The symptom you describe at the beginning was longer and longer processing times with a spinning cursor.
The main reason for that is some kind of conflict that doesn't allow processing to proceed/complete.
This can be due to page faults, permissions issues, font conflicts or corruption.
Open font book and choose all fonts.
Look in the second column and see if any of the fonts have a black dot to the right.
If they do then select a font in the second column go to the edit menu and select all.
Then select resolve duplicates from the edit menu.
Now with the second column still selected go to the file menu and select validate fonts.
Check to see that all fonts have a check marked circle.
Any fonts that have any other designation should have their box checked and the remove checked choice selected.
Data that you keep bringing back could be causing further corruption.
The data that you have saved can be saved on an external device if you end up having to zero your drive and reinstall.
You should then reinstall just the apple software that came with your computer and update.
Turn on file vault without bringing back in data or extra applications.
Then add applications one at a time if you are not having problems.
As to data safety you can encrypt the data stored on the external device by putting it in a folder(s) and choosing to create an encrypted disk image of it.
You do that in disk utility by selecting the folder and choosing new from the file menu.
The choose disk image from folder then choose image.
Then encryption - then save.
You will still be able to unlock the encrypted disk image and get data you may need.
Document what you are adding back to the system if the cleanly reinstalled system is stable.