Comment 18 for bug 550054

In Ubuntu Natty (11.04), you can try this
https://launchpad.net/~patrick2000/+archive/pathos/+sourcepub/1946736/+listing-archive-extra
 ppa
https://launchpad.net/~patrick2000/+archive/pathos/+packages
package, which fixes it for me.

The problem, as I picked up somewhere, is that "xset dpms force on" / "xset dpms force off", which is ~ how gpm unblanks/blanks the screen, affects all attached screens. If the laptops built-in display is not turned off by the *hardware* (without help of gpm), gpm (I think :-)) turns it off via dpms when it is closed. Now if you blank the displays during idle time using dpms, they have to be unblanked at some time again. At that time, the internal display could now unintentionally be turned on as well (if it is not completeley turned of by the hardware anyway). I don't know how/if this is solved in oneiric. Phew... as said: works for me - and probably most other laptops.