Go to the Norton website. Go directly to the Norton website.
Ok, joking aside. Go to the Norton/Symantec website. Many modern "smart" viruses target the things anti-virus programs need in order to function (like active-x controls). Others insunuate themselves into the "sig" files that the AV program uses to determine "safe" files on your computer, and thus overlooks what it is supposed to find.
Go to the Symantec website and do a search for your virus. They will give you specific instructions how to both get rid of it and repair your AV to full functionality.
Good luck. May the schwartz be with you.