Where are my classes?

Hello,

I designed a class diagram. After shutting down netbeans and loading it again, i can't see some of my classes. Of course, I saved the last session. In the project inspector under the category "Project name/ Model" I can see the classes, including operations and associations. But in the diagram they just aren't there. Is this a bug or did I do anything wrong?

[382 byte] By [muelliManni] at [2007-11-26 9:31:15]