XP erroneously changing "artist" data on mp3 files

Whenever I go into "Properties" on an mp3 file and update information (Album

Title, Year, Track Number, etc.) and click "Apply"/"OK", XP will blip the

file and the Artist name suddenly gets extra outlined boxes or other weird

characters added to the of the name. This even happens after I play a song

through Windows Media Player. It doesn't happen EVERY time, but it easily

occurs more than 50%.

I get the feeling there is a registry error in XP, but I honestly don't

know. This started happening after I received a recent critical Windows

update about 3 or 4 months ago.

Can anyone help?

Thanks.