I have an Acer Aspire One AO150 and am having trouble plugging in an external monitor under Ubuntu 9.10. There were no problems under 9.04. If I plug in an external monitor once the machine is already up, then bring up the 'display' application to activate it, it basically hangs. There are no problem under these circumstances if I have desktop effects turned off. I've seen a few mentions of this problem on the Ubuntu forums, but never a solid solution. Any ideas?
A few more details after a question below. The machine does not respond to its keyboard commands to switch to an external monitor, nor does it respond to Ctrl-Alt-F1, etc to switch out of X. The pointer is visible on the monitors (at the edge of each) and is frozen as a 'busy' cursor, but with no animation. The kernel does respond to SysReq commands (REISUB).
In the latest attempt I had the external monitor active earlier, then removed it and activated desktop effects. Upon plugging in the eternal monitor then bringing up the display application, it hangs.