Thanks for posting back with your solution, Christian.
The possibility of a bug exists, but since all of your other menus work, and you indicated that there was a PAR/frame size issue with this one menu, the available data points to the media being the problem, not the program.
However, it is possible that Encore 2.0 does a better job of automatically interpreting the PAR of the asset than CS4. Did you ever try File>Interpret Footage in CS4?
-Jeff
The Focal Easy Guide to Adobe Encore DVD 2.0