I have an Asus G1S laptop running Slackware 12.2 running a custom small kernel compiled by myself.

The problem is as such: Spontaneously the system will crash, i.e. the screen freezes, no mouse movement, if this is a hardware and/or software issue I am not certain. Ctrl+alt+backspace does not reset the computer and the magic system request kernel hack keys does not produce any results.

The logs under /var/log show no errors.

When this happens I simply have to powercycle the computer manually by the power button.

I am not able to reproduce the fault, it happens only spontaneously, either 5 minutes after system boot or perhaps after 2 hours.
There seems to be no pattern, I'm also quite sure it has happened a few times with the wlan turned off.

Any ideas? I don't really have endless hours of time on my hands to see if I can somehow reproduce the error by elimination. The issue also takes place with the stock kernel of Slackware 12.2, however, the issue did NOT take place when I had Debian 4.0 etch installed on the computer.

wild guess:

bad or defective memory?

memtest86 reports no errors.

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.