Mouse stuck in upper left corner.
 

I have two Nforce 939 boards, an Asus K8N and an MSI K9N-Diamond. Problem started yesterday on the Asus board when I rebooted Ubuntu. Tried different USB and PS2 mice and the problem remained. Also, all mice worked OK on a different computer. Figured it was a driver or system problem and I booted XP but the same thing happened in XP. Booted a LiveCD of Fedora 8 and the same thing. I thought it's not a software problem and not the mice, it must be something on the motherboard, so I swapped the Asus motherboard to the MSI. To my surprise the mouse stuck to the upper left corner with the new board. Again I checked XP and the LiveCD and the problem was consistent. So it's not the mouse and not the motherboard then that leaves the video card, the memory, the CPU, and the power supply. I tried different memory and a different video card with no change in the problem. Could it be the CPU or the PS?? What have I missed?

Thanks.

That has to be the strangest problem I have ever come across. You have done quite a bit of trouble shooting already and thats good. Only thing I can think of is try resetting the bios and see if it makes a difference. maybe the ps2 mouse port is sending a false signal.

Are you using a KVM? I had a similar problem (mouse would just die) after switching from one machine to the other and back again. (Solution was to replace Belkin KVM with a Trendnet model)

Fixed!
 

It turned out to be a grounding problem in the motherboard. A friend suggested I electrically isolate and not overtighten the screws that hold down the motherboards. Board's working fine now. Thanks!

Heh, that reminds me of a time I was putting together a system and to my shock I couldn't get it to boot up. In my infinite wisdom I had rested the motherboard directly on top of the power supply. Being a typical power supply, the outer shell was a sheet of steel. And being a typical motherboard, there were all sorts of pointy little metal pins poking down below it, making numerous electrical contacts with the PSU shell the mobo was resting on. Oops!