Cloned gstreamer and gst-plugins-base 20130610. Ran unit tests, and the following tests for playbin fail:

test_uri, test_sink_usage_video_only_stream, test_suburi_error_wrongproto, test_suburi_error_invalidfile, test_suburi_error_unknowntype, test_refcount, test_source_setup

They all deadlock on line 343 in gst/playback/gststreamsynchronizer.c, waiting on a condition that's never signaled. 

The following lines 'GST_DEBUG=2,streamsynchronizer:5  GST_CHECKS=test_refcount make elements/playbin.check' produces the following output:
 
0:00:00.028108833  2458       0xcadd80 DEBUG     streamsynchronizer gststreamsynchronizer.c:800:gst_stream_synchronizer_change_state:<streamsynchronizer0> State change NULL->READY
0:00:00.028206148  2458       0xcadd80 DEBUG     streamsynchronizer gststreamsynchronizer.c:826:gst_stream_synchronizer_change_state:<streamsynchronizer0> Base class state changed returned: 1
0:00:00.028699312  2458       0xcadd80 DEBUG     streamsynchronizer gststreamsynchronizer.c:804:gst_stream_synchronizer_change_state:<streamsynchronizer0> State change READY->PAUSED
0:00:00.028751856  2458       0xcadd80 DEBUG     streamsynchronizer gststreamsynchronizer.c:826:gst_stream_synchronizer_change_state:<streamsynchronizer0> Base class state changed returned: 1
0:00:00.039262243  2458       0xcb10f0 DEBUG     streamsynchronizer gststreamsynchronizer.c:656:gst_stream_synchronizer_request_new_pad:<streamsynchronizer0> Requesting new pad for stream 0
0:00:00.040052190  2458       0xcb10f0 DEBUG     streamsynchronizer gststreamsynchronizer.c:276:gst_stream_synchronizer_sink_event:<streamsynchronizer0:sink_0> Stream 0 changed
0:00:00.040123686  2458       0xcb10f0 DEBUG     streamsynchronizer gststreamsynchronizer.c:291:gst_stream_synchronizer_sink_event:<streamsynchronizer0> All streams have changed -- unblocking
0:00:00.040167315  2458       0xcb10f0 DEBUG     streamsynchronizer gststreamsynchronizer.c:316:gst_stream_synchronizer_sink_event:<streamsynchronizer0> New group start time: 0:00:00.000000000
0:00:00.056724870  2458       0xcb10f0 WARN      streamsynchronizer gststreamsynchronizer.c:381:gst_stream_synchronizer_sink_event:<streamsynchronizer0:sink_0> Non-TIME segment: bytes
0:00:00.056913955  2458       0xcb10f0 DEBUG     streamsynchronizer gststreamsynchronizer.c:341:gst_stream_synchronizer_sink_event:<streamsynchronizer0:sink_0> Stream 0 is waiting

A little debugging shows that two SEGMENT events are received, the first sent by the basesrc when it starts, and the second is sent by the inputselector element when it receives the first buffer, and before it forwards it it pushes pending events, among which is a SEGMENT event. When the first SEGMENT event arrives to the streamsyncronizer it will set it's stream->wait flag to TRUE, because the segment is not in TIME format. When the second arrives it will check if the ->wait flag is TRUE, and if so it will wait for the stream->stream_finish_cond to be signaled, which will never happen because there are no other streams.

Finally backtraces of the threads:

+ Trace 232034