what is the rattling noise from microwave ceilinglass in my neff B6774.ogb?

I have the same appliance and the same problem. Neff know exactly that this problem exists, as when I called them they said "ah, yes, I know what that is". I would like to know if this is something I can fix myself, i.e. if something simply became loose, but I am worried about opening a microwave and have radiation leak out, so will stay away until it stops working.

Leo
October 2010