Comment 71 for bug 969860

I had the same problem for a while now, until recently I found a solution which I'm going to share with you. I know it's not the ideal approach, but I hope it will be useful for you guys until someone fixes the issue.

Investigating I found that installing Caffeine in my Ubuntu 12.04.1 and checking the "Disable Screensaver" option fixed the problem for me. I also checked the option "Start Caffeine on login" at the Caffeine Preference's window, although the "Disable Screensaver" is not a persistent option and each time I log in I have to check this option again.

With this software installed and enabled, my CPU is now always low and the computer is quiet... the only drawback is that the screen never goes blank and I have to turn off the monitor attached to my laptop manually, but for me it's not really a problem and I much prefer this to finding my laptop hot when I come back after leaving it for 15 minutes.

This is the Caffeine file which I have installed:
https://launchpad.net/~caffeine-developers/+archive/ppa/+files/caffeine_2.4.1%2B464~precise1_all.deb

It's also available for other Ubuntu versions as well:
https://launchpad.net/~caffeine-developers/+archive/ppa/+packages