Cube FPS problem

[wouldnyou]

I emerged cube today and have one slight issue, I get big lulls in the game. What I mean by this is while running it goes from normal for a few seconds, to slow for a second. It does this in a sort of loop.
The game shows my framerates in the 400's and it seems normal except the lulls. Even turning down all the effects in the tweaking menu doesn't help. Almost like some process is sucking the cpu for a second every few seconds.
My config is,
kernel 2.4.23 ac sources (ON a laptop)
Nvidia drivers and glx for a geforce4go 64meg card

Other games like racer and such run fine. If anybody has suggestions, I would appreciate them.