Asian characters

Wondering if anyone else has seen random Asian characters popping up in file
and folder names in Vista? I have Home Premium, and every once in a while
I'll notice random letters have been converted - like instead of "sunset.jpg"
it's "s#nset.jpg" where the pound sign is an Asian character. According to
my antivirus (McAfee) I don't have any viruses, and I've scanned for malware
too. I have a sneaking suspicion it might be the Vista Backup corrupting
things while it runs.
Anyone else seen this? How can I stop this from happening?