It is the browser for me, random huge jumps in CPU use, from 15% to 70%.
I have 2.4 GHz and 1 gig RAM.
(firefox 3 and IE7)
The strange thing is this effect is compounded in eastern servers where I ping around 100. The western servers I get about 50 and I don't get as many CPU spikes. I don't see my ping spike and I only get about a 10-20 frame dip (60fps to 40fps) during the freeze.
Maybe because of the refresh time on those stats, I am getting a larger dip but can't see it?
I notice I get this when I play on my restricted account * no pron for youuuu * but not on my admistrator acct.