Originally Posted by Shadow_7
Bad RAM is a common cause. You might also check your video driver / version of X. It sounds like you loose keyboard control at the point of failure. Can you ssh into said computer from another at that same point?
On my current ATI drivers and xorg versions, I seem to have issue if I try to start X without the network in a usable state. I can get around that with -nolisten tcp passed to startx. Although I've been swapping monitors and such, so I've had to rm /etc/ati/amdpcsdb a couple of times. And other ATI only oddities. (bad video drivers IMO). Not that it helps having video drivers that now include audio drivers.
I highly doubt it is a hardware error, if it is, then it does never appear (as of yet) in Windows Vista nor did it ever appear in Debian 4.0 etch.
I have just attempted to install new drivers for my 8600M graphics card in the system, however to no avail, I just got several of the same crashes.
I have not attempted to ssh into the computer (due to no computers readily available at the time of said crashes). Although I must apologize, I forgot to test if the system will power down via ACPI (i.e. by pressing the power button once, then allowing the system to shut down), it does shut down, but the display is frozen until it reaches init 1 -- when entering console mode.
So in other words, the computer has not locked up in ring0 but rather the display doesn't work properly.