I have no clue if this is any help to anyone, but now and then, my screen goes black and I can only see my mouse cursor. On top of this, my cursor and my screen seem to be misaligned, i.e. if I track the cursor to one side of the screen, it will go accross to the other side, but then stop half way through the screen. (I don't know if this is making any sense to you).
The only solution is to hard re-boot from there.
It seems to happen for no specific reason, and I cannot reproduce the bug at all.
No clue if this is any help to the developpers, I just thought I might share this bug.
PS: I am a Linux complete idiot, just an end user and that's that...