when you say, can't access the net, and you mentioned the DNS: can you browse to a site via IP address? Can you ping anything via IP address?
Right-click->manage on "my computer", go to event viewer, check system/application logs, perhaps there is something useful there.
You could also run a network analyser like ethereal on the windows machine and see what the Amiga is trying to do (and how the XP box is responding).
Try removing ICS and redoing it.
- Paul
