Hmm, I think my trust Logitech Trackman Wheel has just bought it. Switched on the mac and the pointer went nuts.

Removed the trackman and tried my graphics tablet mouse and all is fine.
Tried cleaning the ball of the trackman and switching USB ports on the keyboard but to no avail.
I've had to plug in the Mighty Mouse the Mac came with and it's working fine so I'm guessing the trackman has died.
I didn't install the Logitech drivers, it was just the built in OS X ones and they seem to be driving the MM okay.

Is there anything else I could try (plist file to trash for instance) or has it probably had it?

If so, can anyone recommend a good trackball?

My bog standard USB mouse started going nuts a couple of weeks ago - infact it just straight up died. No lights on the underneath or anything.

I had a power cut last week, and since restarting the machine my mouse has suddenly come back to life and no works great again.

Have you tried restarting the machine? (might seem odd for a Mac I know - I never tried it, but if fixed my mouse problems)

I must confess I didn't try a restart but then, the machine was switched on from cold (well as cold as it gets indoors with the current weather) anyway.
Trackball was working fine yesterday when I shut the mac down for the night.