Intel HD3000 video output problem [Solved]

[elvis]

I have an Intel HD3000 integrated gpu on my laptop (cpu is i3 sandy bridge ULV). I have a problem when I connect my external monitor, both with VGA and HDMI output. Honestly I'm not sure that it's an hardware problem, because the following screen is explicative: http://www.abload.de/img/2012-12-09-1355073813jmaac.png

-laptop monitor resolution is 1366x768
-external monitor resolution is 1920x1200
-screen (taken with scrot) is a 1920x1200 image, and is what I see on my external monitor

So the external monitor is using its native resolution, but in a crazy way: the original 1366x768 desktop "replicated" in order to fill the remaining space.

I have no idea how to fix this.
I have no more a xorg.conf to hack, maybe should I create a specific xx-intel.conf in /etc/X11/xorg.conf.d ?

[elvis]

I have found a simple fix: turning off the laptop LCD, and in this way the external LCD full resolution is exactly 1920x1200.

It would be nice to use both screens with their own resolutions, but it is a thing I can live with.