I'm going to put my 2 cents out there, I have been looking at this problem for this past 2 weeks and I've carefully monitored the work load on my pc. What I found was I don't have the performance bog monster until I play about 2 hours of warcraft 3. After that you can clearly see the Warcraft 3 menus moving up and down sparaticly, at that moment everything goes glitchy and mouse movements crazy that exact moment when warcraft 3 for me hits the crazy menu bars movement is when the bogging starts. That's all I really know from now but I can maintain a controlled environment, until I get into warcraft 3, warcraft 3 is a guarantee catalyst to the problem. It's the only application that can cause the mystery system bog monster :P. Hope that helps somehow.

My Specs;

Asus A8N-SLI Deluxe
2GB Patriot Dual Channel 3-3-3-8 Ram
AMD Opteron 180
8800GT

I'm all for someone brilliant fixing this problem!