mouse sticks in corner

Mac mini 1.83 has started to make the curser jittery, then after a minute or two it just goes to the lower left corner. I can move it out, but it just goes right back (after jittering around for a couple seconds). Then I must force quit to restart. After restart I may get a few minutes, but soon the problem comes back. Tried everything I know (zapped PRAM, repaired permissions, emptied trash, re-start, different apple mice, non-apple mice, different keyboards, all updates, no other peripherals attached, etc.). I have not tried disk repair or reloading the system (I would prefer not to do that yet, but I will if I have to).

Curious, but at the same time this problem occurred, my Extensis suitcase (font management software) lost data regarding activated fonts (I went from having about 100 fonts available through Suitcase to about 25).

Curious too is that at the exact same time I started having problems opening files and losing settings in Adobe Illustrator (CS2). I am suspect about running this older Adobe program on this machine - it's always been problematic with occasional freezes.

I'm a 25 year Apple user and graphic designer. I use this equipment to make a living, and am usually good at figuring this stuff out. This one has me stumped. Any clues?