erratic trackball/spinner behaviour

[seaner]

Hi,
I'm experiencing erratic behaviour when it comes to my trackballs.  I've got them hooked up to mouse guts, and I'm running advancemame (0.66?) in dos with the dual mouse drivers.
There are two distinct problems I've experienced...
1. while spinning left, I occasionally hit a spot which I can not spin past (ie. feels like a decrementer getting stuck at 0 instead of wrapping around).
2. (especially in crystal castles) After rolling about normally for a little while, bentley the bear (?) starts leaping around the screen all willy-nilly. (ie. the mouse buttons are triggering, and the X/Y counters are wildly out of control).

This sort of has the feeling of a driver bug, but I thought I'd ask if anyone else has had similar issues.. I'm 99% sure that the problem exists on the PC-side of my setup, since these are working mice which just had their optics replaced with leads to the trackballs/spinner (which are isolated from each other by a switch).

Cheers,
Sean