XP cannot browse after successful authentication

> I have a 5 PC network of all 2000 and xp machines. Same
> setup, they log on to the 2000 server for authentication
> and pull their IP addresses from a linksys router.
> This has been working until today when I installed a brand
> new xp pro computer. Although it successfully
> authenticates to the server and pulls an IP address from
> the router, it does not allow for network browsing.
> Here's the where it gets complicated...If I log on locally
> and assign a static IP using the server IP address as a
> DNS address, then log on to the domain, go back and log on
> locally and switch to DCHP- taking the server address out-
> then log back on again to the domain, it works...BUT, when
> I restart the machine, or log on as a different user, I'm
> back to square one. I've recieved error messages anywhere
> from "Windows has detected a possible security breach"
> to "you do not have rights to access the domain".
> HELP!!!!!!!!!!!