it's probably ioGuiExt, and the overflow is coming from a user with an extremely large number in his stats
- grab
http://home.no.net/addict99/files/ioGuiExt.exe
- replace the one u already had with it.
- execute: site ioGuiExt usertable
- if my guess was correct: check out the userfile where the error appeared, see for any large numbers.