Hej ya!
So, I set up the whole thing like in the tutorial and now the serial output is ok! 
Thanks a lot, Eric!
But:
I traced the lenght and type of 'data' in Flash 8:
data is a string (ok) and the length is 2 (not 1)!
Does anyone know how to solve this problem?
Thanx a lot for your support...
Daniel.