My Ubuntu was running very slow today, so I checked in the system monitor to see what was going on (I only had eclipse and firefox open) and it said that ALL FOUR OF MY PROCESSOR CORES WERE AT 100% USAGE! This does not seem possible to me, and I only had two programs open, which should be using only 2 cores. I looked back later to se that firefox was at 400% CPU, meaning that it was using all four of my cores to 100%. I have no clue what is going on.

ASUS CG Series
Intel Core 2 Quad at 2.66 GHz
Ubuntu 9.10 x64