Mysterious crashes
 

Hi there!
I've been experiencing mysterious system crashes for 4 days now. At first I thought it would be a firefox/flash problem, but it happened again using konqueror or not browsing at all, though I have the impression, that kernel panics or what ever these are are more frequent when using browsers.
When those errors occur, the mouse pointer stucks, no reaction to any keys and the audio device plays the same buffer content over and over again. The only way out is the reset-key.
kern.log.0 seems to have no entries about the crashed sessions at all, syslog contains information about booting time and after, but about the last 30-60 minutes before the crash only says "-- MARK --" in 20-minute-intervals.
My distri is Ubuntu Feisty and the only thing I did before the first crash was installing wlan and the recent package updates.
Any suggestions?
Kind regards,
Philip

have a look on your network, I issue some crashes these last days due to the unstability of my freebox (AC/DC adapter failure).
That's one of the prior cause. Secondly, keep an eye on processor temperature and/or your graphic card, that's enough to hang your system.

CPU temps are observed constantly (mostly <40°C). I haven't found a sensor for my graphics yet, but it's a low- to midrange adapter in a quite cool case ...

EDIT: It might be a coincidence, but after the crashes started on my system I plugged my ext hdd to a friend's Windows machine for video playback and he has been experiencing (reproducable) system crashes of the same kind when playing DVDs since then (no problem before).

Hehe - can be anything :-)

Try memtest first since the RAM is something you actually can test.
As suggested overheating or power supply problems are also common culprits but it could also be something like the mouse or keyboard acting up.

Try booting in a terminal session and run the hell out of the box (make sure all cpus are used) - if it is a power or heat problem that should crash it.
If that works ok your problem is more likely to be somewhere around x (graphics card,mouse or keyboard).

Try to shuffle big files around (from one partition to another) to make sure the hd ain't acting up.

Knowing the hardware you got might help.

Update:
I've run memtest+ and it reported some errors, so I changed my overclocking-settings and ran the test again for 3-4 hours without any errors. After that I started a 12-hour-stress-test including cpu, memory and hdd, which finished without any problems.
But still my system crashes from time to time. The crashes are most frequent when using firefox while listening to music, especially when moving the cursor onto a link.
So I guess my X-server is buggy?

I'd try a different keyboard and mouse if you got some flying around.Had x-crashes because of those loosing connectivity for whatever reasons.

Overclocking the RAM wont do much besides creating problems.

OK, I've found the reason: I've plugged in my LAN-cable and have had no crashes for 3 days now. As I said the crashes started after installing wlan. Any ideas on this issue?

Probably best to open a new thread and explain you WLAN setup there.