Antivirus does not necessarily clean (all) spyware.
You have to run Spybot and/or AdAware. Additionally, you might want to go to msconfig, and check whether there are any unwanted processes that are loading at at startup. How to do this:
1. Go to Run,
2. Run "msconfig"
3. In the Services tab, choose Hide all Microsoft Services
4. Google the remaining items to see whether any of them is malicious
5. Uncheck malicious items
6. Repeat steps 4 and 5 in the Startup tab.
If malicious items keep returning to Services/Startup after reboot, try repeating this procedure in Safe Mode.
(apparently, I miss working as a HelpDesk Consultant...)
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."