My system has crashed twice in 24 hours. These are the first incidents I have had in at least 6 months; I have been rebooting the machine only when a new kernel update came through and it has been thoroughly reliable.
The first crash left a trace in the log; a kernel oops involving a page fault occurred in the middle of the night, and the machine went out of control shortly after I started working on it in the morning yesterday. The second crash occurred this morning. I had been using it for about an hour when kwin stopped responding to most inputs though the mouse would move. I switched to a console and killed kwin, then tried to stop dm. Some kernel issue (an oops or a panic...not sure which) occurred and I had to hit the reset button. Nothing was left in the logs.
After the system came up and I restarted my user session, I started some diagnostics and discovered that I could not dismount any volume and commands such as df and lsof were non-responsive. I dropped to runlevel 1 to do maintenance, but still could not dismount any volumes and still could not use df and lsof.
I rebooted into a usb stick, and went through every volume. I found corruption on the volume containing my system and the one that contained my home. I also found some on the volume that contains /tmp.
What I do not know (yet) is whether this corruption caused the crashes or is an effect of the crashes. The corruption in all cases was incorrect free block count, which is not usually too serious.
So, we will see. I do hope the problem is solved.