Please report bugs to the GNOME Bugzilla, module Rhythmbox.
There are two primary means of communication for Rhythmbox. The preferred method is the rhythmbox-devel@gnome.org mailing list (archives). See the GNOME mailing list web page for more information.
Additionally, Rhythmbox developers and users often use Internet Relay Chat. Just join irc.gnome.org, channel #rhythmbox.