If so I had the same thing with XP Pro.
The only way I got it fixed was I remembered the locations of the icons and made my way to system tools and system restore. I restored it to a previous date and then did a re-boot.
This happened to me twice in a short period of time and I don't have a clue why. It has been over a year now without it doing it again.
I made myself a cheat sheet just in case it happens again.
I rebooted my computer and my desktop icon fonts changed as well as when i open a program or message box all fonts have turned to gibberish. please help!!!