(In reply to Jiri Slaby from comment #3) If sysrq keys refers to Control + Alt + F1 to change runlevel, that's frozen as well. NumLock / CapsLock leds are too and cannot be toggled. Needless to say the mouse pointer also becomes stuck. Sound also stops at the moment of the freeze. For the time being I haven't tried SSH yet, but I assume that wouldn't work either since basically the entire machine stops in place.