funny networking prob

[Harry Kuhman]

I hope someone has a hint for me, where to look for a solution of this.

Yup, I have a hint for you. This problem has been going on as long as this website has existed. It's a very well known problem. I'll move your post to the forum where you can find lots of discussion about it. Here's the part of your post that explains what you did wromg:

I installed knoppix 5.1.1 on one of my boxes harddisks,