I have 2 monitors, 1280x1024 and 1650x1080.
I can run KDE-3.5.9 for a while and after a seemingly random amount of time the taskbar on the 1650x1080 monitor shortens as if it is on a 1280x1024 monitor.
Only the KDE taskbar shortens, the desktop is still 1680x1050.
The other thing is the taskbar on the 1280x1024 screen is set to autohide.
It appears and hides when the mouse is on the 1680x1050 screen.