It's an error message of some kind, fehler = error. I was hoping it would be some sort of popup ad but as it seems something a bit more fundamental, I'll leave it to someone who knows about the innard of computers.
Don't see why it should come up in German though. Do you have a German machine?
I'm very anti-Kazaa and that is most likely the root of your problem. My advice would be to take Kazaa out. There are lots of threads on this and I'm sure someone will hold your hand while you do it. I can't, because I don't know how to and I'm going in a minute anyway.
Hang on for a while and you'll get sorted out by an expert.