i had a smiliar problem mutiple times with my XP laptop, as did a friend. how did i solve it? turned the laptop off and left it for a few days. *shrugs*

you could try manually entering an IP address, DNS etc. which on the main pc you should be able to find by doublcicking on the icon in the subtray on the pc. "support" tab will tell you the IP etc of that computer. change the last digit for an IP for the laptop.

if you're already on manual, them um. i don't know sorry :-\