I have a laptop with a dual head nVidia graphic card. I have two external monitors connected to the docking station. I am running 11.04 (upgraded from 10.10, which was a clean install).
Ubuntu starts on the laptop monitor per default. When I use the nVidia GUI config utility to turn on TwinView (I have the nVidia proprietary drivers), the selected monitor gets a signal as expected, and there is this dialog box which counts seconds I have left to confirm the new configuration. The moment I click OK, the UI freezes. The dialog box doesn't disappear, it remains there, but stops counting the remaining seconds, frozen at "you have 4 seconds left". The mouse cursor moves freely, but nothing responds to clicks or hovering. Normal keyboard inputs aren't recognized either (e.g. Alt+tab). I could never use magic keys on the laptop, because SysRq requires both Fn and Alt gr use, so I couldn't test if this works. There is no way to interrupt the freeze, I have to do a restart from the hardware button in order to get the computer working again.
How can I get this to work? I need it to work from the GUI config, not to be hardwired in the X configuration file, because I often use the laptop away from the docking station, and want it to start on the laptop screen per default.
Update I could reproduce the problem with four different monitors, both through the docking station and directly connected on the laptop's VGA.
Nothing gets written to Xorg.0.log during or after the crash. This is strange, because when I added a monitor to another computer running 10.10, it registered the change as
[ 2823.214] (II) NVIDIA(0): Setting mode [ 2823.215] (II) NVIDIA(0): "CRT-1:1280x1024@1280x1024+2560+0,DFP-0:nvidia-auto-select@2560x1440+0+0"
I connected an external keyboard and discovered that SysRq works after the crash. I was able to kill X and log in again.