I'm using Gnome fallback desktop and no matter what I do, the monitor blanks after 10 minutes when I am watching a video. It does the same thing when I use the Unity desktop as well.

I've installed XScreensaver, but I can't get it to start with Ubuntu. I get "The XScreenSaver daemon doesn't seem to be running on display ":0.0". Launch it now?" but I have tried all sorts of ways on the Web to get it to start automatically and it just won't.