At wits end with intermittant lost WAN connection

[RCtruckRacer]

I have a wired LAN with 3 computers, 2 of which have a rock solid internet connection, and 1 that will lose the WAN connection intermittantly. The one computer that loses the WAN, does have LAN connection. I can browse the network, send and recieve files etc., but it will not go past the router. I have a Motorola cable modem and a Linksys router acting as DHCP. When the one computer loses WAN, the other 2 do not. I can browse the internet all day on the other 2.
What I have done:

Verified that all drivers are up to date and working.
Switched ports on the router for the problem computer.
Switched cables on the problem computer.
Upgraded to the new beta Explorer from v6.
Tried Windows repair connection on the LAN connection.
Removed the LAN connection and made a new one.

I run spy bot and ad aware regularly, as well as McAfee scans. Never found anything other than a few tracking cookies.

When the WAN connection is lost, I can't even get to the cable modem's administration page (192.168.100.1). When I go to the router DHCP list, it shows the LAN address for the problem computer, but there is no computer name on the list. All I have to do is re-boot the computer, and everything goes back to normal. Which leads me to believe it is some sort of wierd Windows XP problem. I have already used one of my 2 free service tags with Microsoft, and would like to keep the remaining one if possible. Can anyone help?

[wolflmg]

Have your tried repairing your connection? Right click on your wireless connection and select repair.

[RCtruckRacer]

Yes, I tried repairing the connection. When that had no effect, I removed the LAN connection and made a new one. That did not work either. Also note, it is not a wireless connection, it is a wired connection (CAT-5)

Thanks though!

[The Wizard]

It could be a fault with the NIC Card.

Try a new card .... they are dead cheap now ... or if you dont mind fiddling, try swapping one over from one of the other 2 PC's.

[pinkice26062]

Have you checked to see if your router's firmware is up to date? Look on the bottom of your linksys router and what model and version# are you using? Now go into your router's web page and see what version firmware it is. You should see it on the upper right side of that page. Usally if you update the linksys firmware, it fixes most problems.