I haven't had a recurrence of the file corruptions since July 2. I did
find preventive measures and remedies, in case you're interested.
The first two involve going to Format>Option Inspector (or
Ctrl-Shift-O), selecting "global" in the first drop-down, typing
SafeFileOpen after the Lookup button, pressing enter or the Lookup
button, and changing the option to "IgnoreCache". Then just a few lines
down, change the ShortBoxForm option to False.
The third is to download the "Corruption.m" package from WRI's site. Go
to http://support.wolfram.com <http://support.wolfram.com/> , select
Resource Library at the top, type "corrupted" in the keyword box, press
enter, and go to the "How do I fix corrupted notebook files?" article.
The specific URL is
I don't recommend deleting Mathematica's preferences (unless it works!),
but the other info there may be useful.
Fourth, be sure to defragment the hard drive regularly. (I doubt this
was a factor in my case.)
Fifth, back up your files regularly. (What a bother!)