High cpu usage when Alice doing nothing

I'm running 2.2, and on a laptop Dell Inspiron 600m Alice pegs the cpu at 100%. On a newer laptop (i5 cpu running Windows 7), it runs at 20-35% for 15 minutes, then goes to 0 for an hour, then to 20-35% for perhaps 60 minutes, then...and so on. This happens whether I'm editing or doing 'nothing', and no worlds are running. It doesn't appear that there's much IO going on. A few page faults here and there, and then 2,000 page faults (all Alice), but not very often. No other program I use uses that much cpu. I regularly run servers and development tools on my system; anything above 5% cpu is out of the ordinary.

Anyone else seen that?

Thanks.

Michael