Sorry to come to the party a little late, but yesterday I didn't spend much time at the 'puter...
I had the same problem late last year, and I too blamed it on ICQ (though was never able to proof it!) - in my case a large number of these trojans installed themselves as *.cab files (self-extracting compressed files)
which my AVG antivirus was not able to delete! Read the logs of your virus-removal, check each and every directory if there are any *.zip or *.cab files of the same (or similar name) and hand-delete them! Otherwise it will come back!!! I had one Trojan last night which must have come through Firefox, and the same thing: AVG removed it, but the zip file stayed behind...
Plus: ever since I'm having some trouble with my svhost file being corrupted, so each night I have to delete a number of files in the c:\windows\prefetch directory or my internet connection won't work the next day... Bloody nuisance!
More
in this thread - and try some "housecall" sites like
http://housecall.trendmicro.com/ Good Luck!