Issue when slowly scrolling down.

Running 10.6.4.

Occasionally, when I scroll down (using the mouse) just a little bit at a time, the screen will jump UP, before scrolling down. This happens quite frequently, but not consistently. It's incredibly annoying.

I thought it was the mouse, so I replaced it with a new one (used to have a Microsoft "Comfort Mouse," now I've got the Mighty Mouse), and it's still happening. My guess is it's some kind of software issue.

Any ideas?

 

Bump. Still happening, still driving me nuts. I'm even considering going back to Windows. Please don't let that happen.