i have double checked and i really do have a Roku soundbridge. and as stretch sais, RSP is installed so it should work.
does anyone else have any suggestions why this problem could occur? the config files of my dektop firefly and my iPhone firefly are identical except for the dbtype. As EVILRipper sais this doesnt matter i can only guess that the RSP version my iPhone runs is too old for the soundbridge.
i will check which RSP version my desktop runs and see if this might be the problem.