tb when joining muc you are talking with
when you are in a convo with a jid and then try to join it as a group chat (for example by right-clicking on it in a pm- or muc-window) you will get:
File "/home/bb/Download/gajim/src/dialogs.py", line 1217, in on_join_button_clicked
password)
File "/home/bb/Download/gajim/src/roster_window.py", line 594, in join_gc_room
if gajim.interface.msg_win_mgr.has_window(room_jid, account) and \
KeyError: u'test@conference.gajim.org'