Norton, hi-jack this, spy-bot (which isn't working properly), ad-aware, um...
Have you tried rebooting?...There is at least one reported server down and this MAY be the problem. Also, can you confirm your operating system? I assume you downloaded the XP 5.03 and not the Beta?
Try shutting them all down and see what happens. If that works, you'll have to turn them on one by one to see where your problem is. If you have Norton Internet Security, not just Norton AV, I'd start there.