Thanks paolo.gai,
I tried both ways, the download of a multiprocessor collection and the seperat download of each program. Unfortunately, the system seems not to care, it is just not working. By the way, in my opinion the download of a multiprocessor collection is just for simplicity so that the user doesn't have to build and download each program separately. IDE also build and donwloads the programs one after another.
I checked all options in SOPC-Builder and IDE twice (and I did already apply the "allow multiple run/debug seesion" options). I can't see any mistake, so I'm stuck and need help PLEASE !!
http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/sad.gif