It sounds like a virus. There's some info here
http://www.gnutellaforums.com/showth...threadid=39612
and point 4 here deals with it
http://www.gnutellaforums.com/showth...threadid=41432
That second thread has a link to norbiesworld. If you go to his site & register (it's free), he'll be able to help you get rid of the virus.
Make sure you have a good, up to date AV program & scan a file before you open it