My linux desktop system freezes (aptosid/debian sid) sometimes and after a reboot I can't find any infos about the reason for the freeze in messages/dmesg/syslog/Xorg.*.log.
When it "freezes" I can still move the mouse in X and sometimes even move the windows for a short time before the system stops responding. Last time I could even switch to the text-terminal and enter my login name, but every text-console stopped after that and displayed no password prompt.
SSH login also does not work after the freeze.
I think the problem started some weeks (maybe 1-1.5 months) ago.
I have a windows partition (win7 64bit) on the same machine which I use mainly for gaming (in the last time mostly StarCraft2). I can't rember any crashes there in hours of playing.
I haven't found a way to force the freeze yet which makes debugging not easier.