I find that when watching a flash video in full screen, if I press ESC key to exit the full screen mode, my screen turns grey and I cannot do anything.
Ubuntu keeps running as I can still adjust the volume with the keyboard shortcut. I tried going to text mode (Ctrl+Alt+Fx) and kill chrome but that didn't work.
In fact I don't know what I have to kill or disable to get the desktop back. The only solution I find is restarting lightdm which is not fun if I had some unsaved work.
This happens on Chrome. The plugin is
Shockwave Flash 11.6 r602
Name: Shockwave Flash
Description: Shockwave Flash 11.6 r602