I don't know if this helps, but when I open stuff on my computer with an AMD 3000+ I get the jumps too. Just now I opened a new firefox page, and it jumped to 92%. I'm running 2 gigs of ram as well.
In Linux, I run this program known as wine, which emulates a windows operating system to play certain games. When I'm playing half life in Linux, my system usage RARELY goes below 95%. Normally it's a steady 99-100% and rarely moves.
There's no place like /home.