EFS Problem

I've been having a strange EFS problem, and haven't been able to find any
other reports of similar symptoms.

The directory in which I store my documents is encrypted using EFS. A few
times a week, I suddenly can't open a file or two - when I try, the
application reports that the file is corrupt, although I can still access
other encrypted files in the same directory. Rebooting resolves the issue.

I've done some testing with this. When I had the issue I copied the
affected file to a USB key that did not use EFS. I rebooted, then copied the
file again to the USB key. I ran a compare on the two files and found them
to be different. It's as if EFS suddenly stops decrypting on a file or two
until I reboot. Also, I've noticed that it almost always happens to a file
I've recently opened and then closed.

Anyone heard of this before? Any recommendations on how to troubleshoot
further? Or perhaps a way to remove and reinstall EFS? I'm using EFS on a
Win XP sp2 Professional laptop which is not part of a domain.