Strange colored lines: wrong monitor resolution

[fuerst]

My DisplayLink connected Apple Cinema 20" worked well using 1.5b3 in OS X 10.6.1 up to today. Strange colored lines and parts of the desktop picture were displayed and the monitor did make a buzzer like noise. Upgrading to 1.5b4 did not help - same result. Somehow I managed to move the Display Preferences pane for the Apple Cinema to the other connected monitor. The resolution was set to 1280x1024 (or x720 - don't remember exactly). Switching back to 1680x1050 solved the problem. It was also necessary to choose the correct color profile.

I never experienced this problem before. Any idea how this can be avoided? How can I change the monitor resolution without using the Display Preferences pane?

Attached is the DisplayLink directory from /Library/Application\ Support