Internet dropped on wireless

Here's a mystery I need help with:

Desktop (JCB1) mysteriously drops Internet connection after a couple minutes. Does not re-connect until reboot of card.
Yet maintains network connection to home network =ALWAY SOLID.

Home Network=
Cox Cable modem -to-> Belkin Router (4 Cat5 connections)
Belkin Router
| |-to-> wired to Accesspoint -to-> (1)wireless JCB1 Dell Desktop Computer
| | . . . . Accesspoint also -to-> (2) wireless MDB Dell Laptop
|
|-to-->Wired to FireplaceDell

The MDB laptop never drops connection to either Internet OR home network.
But the JCB drops its wireless connection to the Internet Every time!


I have re-set everything multiple times,
changed the wireless card (brand new) in JCB1,
and re-installed drivers.

Wireless Channel is the same on all,
IP address is DHCP through the Belkin Router
There are no interference issues (2.4ghz phones, microwave, etc.)

All systems running Windows XP Home;
Internet is ROCK SOLID on all other PC's connected to the Router and/or Access Point.

Any suggestions?

cbowman