As well as the aforementioned flicker problems I also have lost the entry boxes for my login screen. (I can bypass the problem if I use automatic login, but then can't logout). The input box is still there, (though hidden) I can sometimes guess roughly were the input box should be and type blindly and still get in.
The problem is resolved if I uninstall DisplayLink Driver.
Here is a macrumors thread from other users who have a similar problem:
http://forums.macrumors.com/showthread.php?t=1191946
Your help would be appreciated.
Mountain Lion
DisplayLink_Installer 1.8