Genie animation running slow

The genie animation when I minimise a window has started running slowly all of a sudden. By slow I don't mean slow motion - it takes the same amount of time, but runs at about 5-10 frames per second.

I'm running 10.4.10. CPU usage is virtually 0% when it occurs.

Does anyone know what might be causing this? Thanks

It's a 2GHz C2D Macbook. I've tried it with no apps at all running and it doesn't seem to make any difference.

I shut the computer down a few times each day, and that doesn't help either

Other animations work fine, like the dashboard ripple effect - it's just this one really. If I change it from genie to scale effect, it's still slow.

Well, just in case anybody else has this problem, I managed to fix it.

I downloaded Onyx, ran it, then changed the minimise effect to 'suck' under the dock settings. All of a sudden it's running at full speed again, even if I change it back to genie.

No idea why this would fix it - I didn't change any other settings.