My two displays are:

• Intel GMA x4500 Laptop (1280x800 native resolution of the built-in display)
• External display (1920x1080)

A few minutes after I login to my dual monitor setup, it gets reset to mirror screens. If I restore the settings via the displays application, everything is fine. On each reset, the following messages are written into /var/log/Xorg.0.log:

[    60.852] (II) PM Event received: Capability Changed
[    60.852] I830PMEvent: Capability change
[   132.920] (II) intel(0): EDID vendor "SEC", prod id 12869
[   132.920] (II) intel(0): Printing DDC gathered Modelines:
[   132.920] (II) intel(0): Modeline "1280x800"x0.0   68.94  1280 1296 1344 1408  800 801 804 816 -hsync -vsync (49.0 kHz)
[   134.228] (II) intel(0): Allocated new frame buffer 1280x800 stride 5120, tiled

Whereas right on startup or manual resolution reset, /var/log/Xorg.0.log reports the expected frame buffer allocation:

[  1562.382] (II) intel(0): EDID vendor "SEC", prod id 12869
[  1562.382] (II) intel(0): Printing DDC gathered Modelines:
[  1562.382] (II) intel(0): Modeline "1280x800"x0.0   68.94  1280 1296 1344 1408  800 801 804 816 -hsync -vsync (49.0 kHz)
[  1576.740] (II) intel(0): Allocated new frame buffer 3200x1080 stride 12800, tiled

Is Ubuntu 12.04 not compatible with my video card?

Can this be solved within Ubuntu?

I like its interface, but manually fiddling with resolution on every login is not bearable.