Same here on openSuse. The control panel should stick to the left side of the screen, but if a window touches the left border of the screen, the control panel moves to the right side of that program window. I'm using KDE 4.8.1 on openSuse 12.1, but I had that behaviour earlier on e.g. KDE 4.7.
Happy to find some people who have the same trouble, gonna file bug report on some kde side.
Please post if you find a solution.
EDIT: Filed a bug report here: