Belkin Router + Sweex Adapter problem

Setup:
- Broadband connection with Belkin Router
- PC A (XP Home Edition) has Belkin USB Adapter; can connect to the Wireless
LAN and can connect to the internet
- On PC B (XP Professional Edition) I've installed a Sweex Wireless USB
Adapter; after some tweaking it says "connected to WLAN", so thats good, but
I cannot get the thing to connect to the internet.

I've correctly confiured all B's broadband proxy settings (same as A), setup
the default gateway as the IP address of the router, and entered the DNS
addresses (since he didn't auto-detect them). After a while, B gets
assigned an IP address like he should, but connections outside just don't
work...

A can ping to the router IP, B can't...

Any idea what I can check next?

thanks

Sam
ps: XP Firewall is disabled on both machines