Dell 1370 does not allow access only to SOME sites

Hello everybody,
 
One of our laptops is experiencing an issue that goes beyond my troubleshooting ability.
The laptop is an Inspiron 2200 with XP Home SP2.  The issue revolves around the built-in Dell Wireless 1370 WLAN Mini-PCI Card.

A week ago some sites have begun not loading.  One example, the login into dell.com does not work.  After typing in the credentials and hitting submit the browser stalls and ends up with a page not found error.  Similar things happen with Yahoo mail and when posting into Craigslist, to cite only two. 
 
This is what I have done so far:

1 – Scanned with SpyBot, AdAware and Norton AV.  Nothing was found.
2 – Hoping in for an Internet Explorer issue I tried with Firefox and the problem were there.
3 – I downloaded the most recent driver for the card from Dell and used to upgrade.
4 – Step 3 did not work so I uninstalled the whole card from the device manager and reinstalled the new driver.  No luck.
5 – To try to pinpoint the origin of the issue I have tried disabling the wireless connection and enabling a wired connection to the same router.  The issue was not present.
6 – Taking the prodding further, I disabled all connections and installed an old D-Link DWL-650+ PCMCIA card.  The problem did not show and navigation was flawless.

I believe this problem is linked to the 1370 card as other connections work just fine. 

I ran out of ideas to troubleshoot this issue.  Anybody knows what may be happening?

If the card is bad, how could it not load only some sites and work fine for all the others?

Thanks!