It works now! Thanks for the help.
I used the Debug pipeline before, but that didn't give me any errors.
But I than used the gears demo as you told me, and that worked.
So I added my shader class to that and at least I could create the shader. I found a few more little bugs that I than removed, so that it works now!
I just have to figure out what exactly the difference ist between the gear demo and my programming...
I'll let you know, in case someone has a similar problem.
(btw. how do I activate this javadoc for intellisense in netbeans 5.5?)