Well I think this is halfway my fault, because I didn't checked the depencies before I installed something, but I think there must be some weird dependencies with some packages.
At first I just wanted to configure firestarter, but it said that it needed libgnomeui to show the configuration-screen. So I installed it and it worked fine. After some time I noticed that Nautilus was installed too and since I didn't want Nautilus I removed it with slapt-get. But with Nautilus slapt-get removed firestarter and Firefox too (maybe some other programms too and I just didn't noticed now).
Well after I noticed Firefox was removed too I reinstalled it ( version 3.0.8 ) and now I have Nautilus again and there are even Icons on my fluxbox desktop
How can I delete Nautilus and the Icon thing (don't know which lib is responsible for the Icons) without deleting firefox?
PS: and Firefox likes to crash without any reason now