Oh yeah... Actually error is "Kernel Panic has occured, switching back to text mode" the whole system freezes and I have to hard reboot.
do you know about the alt+sysrq key ... raising elephants is so utterly boring http://en.wikipedia.org/wiki/Magic_SysRq_key#.E2.80.9CREISUB.E2.80.9D_.E2.80.93_safe_reboot
if you can get the kernel trace out of dmesg or setup the kconsole, paste it. we can probably shed some light on what's happening if you can get the trace and the message.
regarding overclocks .... i totally disagree with a lot of what has been said. How can a layer of software on top of a cpu make any difference with regards to the stability of the cpu. Sure, it might have different usage patterns to make instability more or less likely to show up; but if your clock is stable and the instructions always make it across properly, the code running on top of it has nothing to do with the fact that that piece is working right or not. If your clock is unstable, it's purely a hardware problem.. Software X won't like unstable hardware anymore than software Y, even if X is pure gold and Y is garbage code. You may get lucky for a bit, but it will eventually show up regardless. Edited by lloyd mcclendon - 1/11/12 at 10:13pm