In Maverick, under the System>Preferences>Main Menu, the Sound & Video entry has two listings in the Items list for Rhythmbox Music Player. The only difference I can see is that the first entry has "rhythmbox %U" in the 'Command:' textbox of the Properties window, while the second has "rhythmbox-client --select-source %U".

Does anyone know the reason for these two different entries? Thanks for reading, Hugs.