Safari repeatedly trashing Other Forms data

Question

Any idea what would cause Safari 5.0.4 to repeatedly trash the data in the Form Values file? It seems to affect only the Other Forms data (not the passwords). I can easily restore from yesterday's backup and everything will work normally for a while, but within a few days, the file will be munged again. The corruption seems to occur either during a Safari Quit or the first Safari launch of the day (at least most of the time). (No odd plug-ins.)

Answer 1

I continue to have this problem with Safari 5.0.6 (and can't upgrade to 5.1 because it's Autofill feature is useless). Two days ago, my Other Forms file (in User/Library/Safari) lost most of its data 8 or 9 times in about 5 hours. The file would go from 512KB to 24KB or 72KB. It would still have maybe a dozen or two entries, but all the others (several hundred) would have disappeared.
I would quit Safari, restore the Other Forms file from my backup, and relaunch Safari. All data would be there. A half hour later, it would have disappeared again. Each time, I choose a slightly older backed up file. Eventually, the deletions stopped and, for the past 2 days, I haven't lost anything, but I know from experience that it will happen again.
Apple doesn't have any clues and has nothing to suggest. I've run diagnostics but found nothing. Disk Utility finds no problems. Everything else works fine. Weird.