Macbook internal camera invisible...

I need some advice how to get my internal camera going. Its most likely not Max related.
I had it running in the past, but in the meantime I updated to OS X 10.6.3.
In Max I get a -9405 error, and the strange thing is, the device list shows 7 devices:
"DVCPRO HD (1080i50)", "DVCPRO HD (1080i60)", "DVCPRO HD (720p60)", "DVCPRO HD (720p25/50)", "DV Video", "IIDC FireWire Video", "USB Video Class Video"
non of them works, but I have only the internal camera (Don't know how it should be called).
Other programs like skype are not able to access it either. I get a "no camera" explanation...
What else can go wrong? I can't imagine, that the camera is grabed by another process, as the lights of the camera are not illuminated...