When using USB Overdrive to accelerate the tortuously sluggish mouse speed of the OSX default, do you experience a quixotic pointer that seems to jump and jiggle about on its own from time to time?
The solution, by no means self-evident, appears to be simply that the "wheel" setting must be set to "no button". Wheel-scroll up & down will still work. Thus setting to rest months of irritation and fiddling around.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040302194850369