Just a note I thought I'd toss in here...

I have a 2nd system that is nearly a clone of the first, it's an x2 5600 with a nvidia 7600gt... I've been using that to run 4 of my 5 box team. Yesterday my girlfriend left a lot of browser tabs open with her job search, so I didn't want to close them... but once I got all copies of wow running 3 of them ran fine, the 4th ran like crap.

I closed out the unneeded applications and boom, everything was smooth again.

It's pretty amazing that it's that borderline!