For now, why not try dis-abling norton and running something *like* AVG:
www.grisoft.com - just as a "second opinion" on that virus. As you said, there was a conflict between VPOP & Norton when you installed it...maybe the problem is spreading further than first thought.
Anyway, for now try another anti-virus package make sure it is active and then dis-able Norton - try running VPOP without Norton.