It jitters quite a lot even though I'm not moving the mouse.

I thought you meant that it sometimes left graphics blitter behind when you drag it across another window.

It shouldn't jitter at at all when you hold the mouse still, it doesn't do that on any of my systems. The only way that should happen is if the mouse itself is sending jittery data to the application (lots of one-pixel mousemove commands even when you're not moving the mouse).