I did not solved the problem above, but I find out the reason of it:
If my Webcam is plugged in there is obviously some conflict with the soundcard. The Webcam is a Phillips PCVC740K ToUcam Pro. My soundcard is a Sounblaster Live. If I plug in the Webcam after Booting everything works fine. So the problem is no longer so important.

But if anyone knows to solve please tell it to me!


PS: My printer over usb is working fine with knoppix ... so far so good