Hi! I'm currenlty helping a person who seems to be having advanced problems with his VLAN NT network. The issue/problem is shown below:

Question is shown below
After setting up an additional VLAN on our NT based network clients are no
longer able to get out to the internet, and the problem is not restricted
to a particular subnet. But I can take another PC plug it into the same
port and get out to the internet. I don't suspect our AT@T hosted DNS
server, because some clients are having no trouble. We are using 3com
switches and hubs and a 3com 3500 corebuilder fiber backbone.

Now, what could be wrong with his network?