Yesterday, while upgrading a friends 98se to Xp Home, I ran into a problem with a recomended update from Microsoft.
Update for Microsoft Windows XP (KB826942)
Download size: 275 KB
Wi-Fi Protected Access (WPA) support is now available for Microsoft Windows XP. This update provides additional wireless security capabilities for the latest generation of wireless networking equipment supporting WPA. After you install this item, you may need to restart your computer. Read more...
This caused a DNS error when it was installed. Their computer is attached to my wireless LAN via a USB wireless antenna. This was working excellently untill I installed this patch (along with 17 others, unfortunately). After installation, the IP address changed and also the MAC address.

Repairing the connection would not cure the problem, and manualy inputting the correct addresses didn't work either.

After alot of trial and error searching, I found the culprit.

My laptop has had a reoccurrance of a similar problem, but just when I have had dial-up and wireless capabilitiesn installed at the same time. So I have been removing the dial-up connection any time I wished to use the WIFI capabilities of my laptop, and then reinstalling the dial-up when I didn't have a WAP available.

To test if this was the problem in my laptop, I installed the dial-up connection while still using the wireless capabilities, and immeadiatly had a DNS failure. I then took the update out by using the 'Add/Remove' program option, and after a reboot (mandentory) it worked fine again, with wireless, ethernet, and dial-up.

This update is a roll-up of several WIFI updates, but it is the only one that is causing the problems. The updates that make up the roll-up of this patch, all work just fine by them selves.

Note: Twice while testing with the patch still loaded, I had the correct IP and MAC address, but was still getting a DNS error.