corrupt files in the PyMEL cache folder

[cspears]

I have had a really strange issue pop up with PyMEL.  In my studio, users set their PYTHONPATH to a folder, so they can load up all of their tools.  We still have users using Maya 2012 and PyMEL 1.0.6.  About a week ago, artists were having trouble using the environment.  Their tools were not loading up.  I tracked the error down to a file:

pymel/
    cache/
        mayaApiMelBridge.zip

Replacing the file with a copy from a backup environment fixed the issue.  I think the file must have somehow gotten corrupted.  Does anyone know what the files in the cache folder are for?  What writes to that folder? 

I am worried because I think the same issue might have popped up last year (to the day actually) because I saw a file called _mayaApiMelBridge.zip that was modified about a year ago.  My guess is that the same file got corrupted, so someone renamed it.  Then either a new file was generated or a replacement was simply copied over.

Thanks.