Comment 9 for bug 1318403

I can confirm that. Still happens with Ubuntu 15.10 and Firefox 41.0. I needed a long time to find out that Firefox causes it.
Deleting .mozilla folder and disabling add-ons doesn't help. Whenever I use for example Midore and keep Firefox closed, no crashes happen.

I don't have Adobe Flash installed and only use bcmwl-kernel-source as proprietary driver (graphics are Intel HD).
Unfortunately I have to use the power button to reboot the frozen system and don't have any error logs. Caps Lock button is not blinking (which usually is an indication of kernel panic).