Hi,
please read the link "VirusRemoval" below in my sig and:
- post a hijackthis-Log for diagnosis
- tell us WHERE exactly avast finds the trojan (full path/folder/filename)
- try ad-aware, spybot & cwshredder
- scan the infected file Online with Trend, RAV & KAV for better identification of the variant
- secure your system & browser better..