Norton has never saved me from trojan outbreaks. Ever. I frequently use Housecall - which i believe dtb linked above... And Symantec also has an online scanning program which is often more up-to-date than installed software.
Amp up your firewall settings and if you're not already doing so.. I would suggest not using IE, Outlook, or Outlook Express. We used to have many many problems with trojans and viruses until we switched to the Mozilla suite for email and web browsing and kept ZoneAlarm running.
If you have men who will exclude any of God's creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men. -- St. Francis of Assisi