reboot low graphics mode screen shut off problem

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http://www.linuxquestions.org – Okay, the problem is twofold and it's driving me nuts. To start with, if I don't use the computer for a length of time, the screen goes black and I have to reboot. Now, I've shut off (as far as I know) the screensaver, the power management is set to not shut off the screen but either I've got those settings wrong or I'm missing one? I like to set my puter to watch a video at night to fall asleep to but before the movie is done, it goes black (and I have to reboot). And that leads to the second problem; when I reboot, 1/2 to 3/4 of the time, I get the dreaded "Ubuntu is in low graphics m (HowTos)