The lines you entered above will make get_iplayer print some additional info and then quit before actually attempting to launch rtmpdump. The additional info should show the output from "rtmpdump --help" (if any) that get_iplayer is attempting to parse.
At the end I can see the following lines: ANDA1 -> -1 ANDA2 -> .\RTMPDump\rtmpdump.exe ANDA3 -> _______________________________________________ get_iplayer mailing list [email protected] http://lists.infradead.org/mailman/listinfo/get_iplayer

