Plant Explorer Problem

The system is 800xA V6.0.1 with german language pack. If I open Plant Explorer or Engineering Workplace it work well but after some time I have an issue:

If I select an aspect in the right upper window then the content of the right lower window don't change, it is frozen. A the "Edit" function for graphics still work, but e.g. the "config view" of a faceplate don't. Only solution is to restart the WP.

Has anyone faced this issue? What could it be?

Thanks in advance

/Erik