Internet connection keeps disconnected

guys,

Need some help here.
Situation is this:
This client has a very small w2k server based domain network. Everything is fine including DHCP, DNS, WINS, RAS, AD... All works fine until... CLIENT WORKSTATION, not the server loses internet connection. Funny thing is even when workstation loses Internet connection, its IP is retained and LAN side works fine - connection to the server and other resources like net printer and such, are all working just fine.
So, what do we have to do to make internet connection work again? All I have to do is run a IP renew batch - even tho that IP is perfectly fine...
When it renews the ip, it gets the sets of ips, DNS, WINS...

One thing I noticed... Very important, is that when the clients go to certain sites, like bank site or some randome sites, it does this. As soon as they go to these sites, they lose their internet connection and have to run the IP renew batch.

so... any ideas?????

thanks