I have noticed a new problem as of late on my 1.83GHz white MB. OS is 10.6.8.
My hot corners for Exposé will randomly stop working. The F keys I have set up to access the different views still work, as does Dock Exposé. Restarting the Dock process manually (from Terminal or Activity Monitor) doesn't fix it.
When this happens, another symptom appears - my trackpad suddenly starts using Drag Lock (even though this is definitely disabled) and won't UNLOCK once it starts dragging. Hitting Esc several times gets it to stop with some applications (like Firefox), but with others (like MagiCal), I have to kill the application entirely - and the symptom persists after the application is restarted.
The only way to fix it is to either put the machine in standby or reboot it.
And, oddly enough, when I try to put the machine in standby by closing it, it doesn't actually go to sleep - the fan stays spinning (and it's at max speed, btw) and the sleep LED stays completely lit (no pulsing). If I open the display, it actually goes to sleep completely.
It's a weird set of issues that I haven't seen before, to say the least. It's also annoying as hell.