sudden, unpredictable blank screens

[Alan Chang]

Once in a while, when I am logged in and using the computer, the screen will suddenly become blank. (Sound still works -- I know this because one time the screen went blank when I was watching a video.) At that point, I cannot do anything except turn my computer off by holding down the power button.

I am running Lubuntu 12.04 on a Macbook Pro 6,2. (I have tried this on Lubuntu 13.04 -- had the same problem.)

[Alan Chang (glyxeon)]

One thing I've noticed: the last two times that this blank screen occurred, the following had happened right before it:

(1) My computer screen was blank (because of xscreensaver, probably?)
(2) I type my password to unlock the screen
(3) The session resumes, but immediately goes back into screensaver mode again
(4) I type my password again
(5) The session resumes. I am able to use the computer for a few moments before the screen turns blank again. This time, nothing I do can get the screen un-blank.

[Alan Chang (glyxeon)]

Actually, it might not be related to the screensaver, because this problem has also occurred a few minutes after logging in (with the computer in use).