Network works one day, fails the next mixed Vista XP

> My new Vista PC wont work with my Belkin PCI network card, so I created a
> network where the XP PC connects to the wireless router and the VISTA PC
> connects to the XP PC. The XP PC was setup to allow internet sharing and
> everything was dandy; I could connect to the internet from the VISTA PC.
> Day 2 I power up XP PC and VISTA PC, exactly the same and I get the yellow
> warning tringle to say network connectivity between XP PC and VISTA PC is
> limited or unavailable. Tried setting the IP addresses manually, tried a
> different cable. Tried using an XP laptop that connects to the same
> wireless
> network (replacing the XP PC), nothing seems to work.