If it is a Browser Helper Object(BHO) that is doing the redirect then Hijackthis should clean that up.
http://www.download.com/Trend-Micro-...-10227353.html
Close all other programs, install HJT and then click "Do System Scan and Save a Log file"
It will list all kinds of switches and programs that determine how your computer behaves. As a start, select all BHO and click "FIXED CHECKED". Becareful with the other items HJT finds as some of them are needed for your computer to run. Removing all BHO should not an issue but yahoo toolbars etc will be missiing but you can always install them again as needed. The object today is to get you browser to goto your AV home to update definitions. If your current AV does not fix it try AVG Free AV at:
http://grisoft.com and search there site for "FREE" and try the free version, very nice.
If that does not work and you have the time, try the HJT upload service, it may take you further.
Keith