So, looks like it's trying to boot up on crtc #3, but presumably only 1 and 2 are attached. That happens well before X.org loads, so it looks to be a bug in kernel drm.
Please turn on kernel graphics debugging - run 'sudo xdiagnose', it's the first checkbox. Check it, click apply, reboot, and reproduce the problem, then collect 'sudo dmesg > dmesg.txt' and attach that here. That will help identify why the kernel is getting so confused by CRTC #3. There's been a significant amount of kernel work upstream to resolve problems like this in sandy bridge and ivy bridge, and presumably if you boot the 3.2 kernel the issue would be resolved. If you'd like to test this theory but you don't want to install Ubuntu Precise, it should be sufficient to boot a Live USB session, configure the monitors, and see if it is working properly now. You can get the current Live USB desktop image at http://cdimage.ubuntu.com/daily-live/current/ and create a USB boot drive using usb-creator. ** Changed in: xserver-xorg-video-intel (Ubuntu) Status: Confirmed => Incomplete ** Summary changed: - [snb-m-gt2] Ubuntu won't load with external monitor connected on ASUS N73SV laptop. Dual monitor bug. *ERROR* Couldn't find PLL settings for mode! + [snb-m-gt2] Booting with external monitor fails with *ERROR* Couldn't find PLL settings for mode! -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/814895 Title: [snb-m-gt2] Booting with external monitor fails with *ERROR* Couldn't find PLL settings for mode! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/814895/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp