XPS 400 no immediate network connection

I'm running WinXP-Pro SP2. My XPS 400 takes about 5 minutes to connect to either my LAN or the internet after I first login. Once it connects there is no problem unless I switch users or log off. Then it again takes time to re-establish the connection. If I try to connect to a website, nothing will be found. I'll open a DOS window and ping a host until I get a response. Once I do the browser works as does Outlook. No other system on the LAN has this problem nor was there a problem before I bought the XPS 400.

Suggestions?

Thanks.