As I've said on Tuesday, the last VirtualBox crash corrupted anything related to X11.
After two days and reinstalling nearly all libraries I could got the KDM/GDM working, but the is still one thing missing: the KDE menu button.
I don't know which "launcher" has failed and the logs aren't helping either. The other icons with "?" are ok because they are used only in clients who log in using NIS (a mount their homes via NFS).