Mouse Jumps

[wynnwill]

My new Logitech optical USB wheel mouse occasionally
jumps erratically on my Toshiba Satellite 2435 portable.
I can't track down the problem, but here are clues:
1. I've tried two identical mice and three different USB
sockets. All bad.
2. I've installed and uninstalled both the Toshiba mouse
software and the Logitech software. Still bad.
3. I used msconfig to deactivate all startup programs.
Still bad
4. I've reloaded the mouse driver and replaced it with a
driver for "HID compliant". Still bad.
5. I've tried turning my touchpad off. Still bad.
6. The jumps only occur when I move the mouse.
7. The jumping gets worse the longer the computer has
been on.
8. The jump is usually to bottom left corner, but not
always.
9. Jumps seem to occur with all software
10. I have not seen jumps with a Targus optical mini-
mouse.
11. I'm using XP home.

Any suggestions, please?