After SP2 install, browser use hangs PC

After installing SP2 on Windows XP, I have a new, debilitating problem: whenever I open an application window that contains HTML and/or images, my PC hangs, most often when scrolling the window but also sometimes when resizing it or when loading new content from the web. I have experienced this behavior with IE-6, Firefox, and even an Outlook mail message in HTML format with pictures. I have also had the system hang when scrolling in Excel and Word when there is an "inactive" browser window open in the background.

When I say "hang" I mean dead-stop: no cursor blink, no response to mouse or any keyboard keys, including things like Caps Lock. I have to hard-reset the PC to reboot.

If I reboot and never open a browser, the system works fine for as long as I am willing to test it (hours). But once I open a browser it seems to immediately become unstable. Though the problem appears to happen at random times, it is pretty frequent, usually within 5 or 10 minutes of the last reboot or browser open, sometimes within seconds of opening the first browser window after reboot.

I have scrubbed my machine for viruses and spy-ware (AVG, Ad-Aware, Spybot), and use Zone Alarm as my firewall.
All windows updates are in place and verified.
I have the latest BIOS loaded.
I have run memtest86+ for 9 hours and it has come up clean.
I have a relatively new disc (< 1 year old).

Any help out there would be MOST appreciated!

 

And the answer is…Video Driver! Apparently SP2 is compatible with only the latest ATI driver for my laptop. Discovered a newer one, updated, problem gone!