(I'm forwarding this bug, don't have the hardware/bug myself to report)

There are >20 people reporting a problem on Ubuntu when using a kvm switch and it losing the correct resolution; the reporters have varying video hardware (Intel, and Nvidia) and they're saying it's only affecting Gnome desktops.
The details are a bit sketchy; the screensaver seems to be common among most of them - see the various reports at:

https://bugs.launchpad.net/ubuntu/+source/gnome-screensaver/+bug/988290

They're generally reporting that running 'xrandr' sorts it out (with no parameters).

To quote the original reporter:

  I have a machine that shares monitor, keyboard and mouse with a second
  machine via a standard KVM-Switch (USB/VGA). After updating to precise beta 
  yesterday, I noticed that, after having worked with the other machine for a
  while and switching back to the precise machine, screen resolution has 
  changed to 800x600. Just opening "Monitors" from gnome-system-settings 
  restores the original resolution of 1280x1024, you don't need to change 
  anything.

  This is reproducible, if you switch away from the machine long enough (I 
  guess until the screensaver gets invoked) resolution will be changed when you 
  come back. This was not the case with oneiric.

It was originally assigned as an X bug, which got rejected on the basis that it was the kvm not being nice enough to kick the host (which is my reading),
however the fact it's working with other desktops make me a bit confused.

Perhaps doing an randr probe when the screensaver wakes up would solve the problem?

Dave (just triaging some bugs)