Problem with New WiFi Network (Belkin)

Hi,

I'm having a problem with a newly home office network. If anyone can
help, it's probably something very elementary that I'm missing.

I have my DSL service coming in from the wall to a Cisco 678 (PPP mode).

This Cisco 678 is then connected to a brand new Belkin DSL Router/54g
Wireless Access Point.

So far so good.

Now, my PC (Win2k pro) is connected to the Belkin with an ethernet
cable, and it can surf the net perfectly.

However, I also have a notebook running XP Pro. I put a Belkin 54g
wireless notebook card in it and while it says it's connected to the
wireless network, it can't ping the Belkin, it can't access the Internet
and neither it nor my Win2k pro machine can see each other across the
network (file sharing is enabled on both machines).

I also tried hard-wiring my notebook to the Belkin, and the it also
seemed to think it was on the network, but still couldn't ping the
Belkin or go on the 'net.

Any ideas before I try, what I assume is the slow, unhelpful and
expensive Belkin support route?

Thanks.