unexpected restart of computer

[Cybe R. Wizard]

On Sun, 03 May 2009 09:23:39 -0500
Wade Smart <wadesmart at gmail.com> wrote:

> 20090503 0920 GMT-5
> 
> In the past 24 hours, 3 times now my computer has rebooted.
> Well, thats not entirely accurate...
> 
> Just 2 minutes ago I was reading a article on a web site, I moved my 
> cursor up and to the left to back out of that page and my screen 
> instantly turned black. It takes between 5 and 10 seconds and then
> the login screen pops up. So the computer hardware isn't rebooting,
> only the OS.
...
> 
> Wade

It seems that only the X windowing system is dying/coming back up.
Have you installed/begun using/changed Compiz lately?  Do you do any
other CPU-intensive stuff?
Do you have hardware monitors to let you see your internal temperatures
or fan speeds?  Those are the culprits I would first suspect.
Check the insides for dust build up, check fan speeds and HD/CPU temps.

Cybe R. Wizard
-- 
Registered Linux user # 126326
Registered Ubuntu User # 2136