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I recently upgraded from Maverick to Natty and this problem has appeared after the upgrade - it never happened while I was on Maverick.

I'll try to explain this as well as I can.

On Maverick when I plugged/unplugged the external display to my laptop I had to manually enable/disable the external display from the Monitors dialog.

By Monitors dialog I mean this:

enter image description here

But on Natty, when I plug/unplug the monitor this is automatically detected and the display is enabled/disabled, without me needing to go that Monitors dialog and do anything. I think that the OS does some polling of the external display port to see if something is plugged.

My problem is, when I have already plugged an external monitor and am using it, sometimes it becomes disabled by the OS, as if I had went to the Monitors dialog and disabled it manually, only I didn't do anything, I am watching a movie and I'm not near the computer at all. I think that this autodetect feature disables it. It seems that it thinks that I have unplugged the cable, even though I haven't. I think that the VGA cable doesn't make good contact with the pins in the laptop's VGA port so it might be disconnecting for a fraction of the second, but this wouldn't be a problem if there wasn't this autodetect feature.

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Try Caffeine to keep your monitor on, use these command in Terminal.

sudo add-apt-repository ppa:caffeine-developers/ppa

sudo apt-get update

sudo apt-get install caffeine

Caffeine is used to supress any power saving mode from being turned on; e.g. When you're watching a film and the screen goes into idle mode.

I use Caffeine myself and think it's brilliant.

share|improve this answer
My problem has nothing to do with screensavers or power-saving. If it were because of that, the primary monitor would be affected as well, and it is not. – sashoalm Aug 2 '11 at 14:20

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