Buck - man, that's a strange one... and unfortunately one that I've run into alot with XP and even with Vista.
The problem is usually a program that has a memory leak that doesn't show up in task manager and therefore you can't trace it. I've narrowed it down to a few different programs on my machine over the years. Usually these are fixed with upgrades, but sometimes they are not.
Try this - when you are going to play WoW, restart your computer first. Start up WoW from a fresh desktop before you've run any programs. If that works, then chances are it is a program on your computer that you didn't run before playing.
If that doesn't work, then it may be a program that automatically starts up when you start your computer. Check those out and turn them off one at a time to narrow down the culprit.
These tips might help, but it might be something else funky going on. Give these a shot and see what happens then let us know. We can offer further stuff to try from there. Good luck!
