Here's the dpkg output:

ii  bluez-gstreamer                            4.12-0ubuntu5                           Bluetooth gstreamer support
ii  gstreamer0.10-alsa                         0.10.21-3                               GStreamer plugin for ALSA
ii  gstreamer0.10-ffmpeg                       0.10.5-1                                FFmpeg plugin for GStreamer
ii  gstreamer0.10-fluendo-mpegdemux            0.10.15-1                               GStreamer plugin for demuxing of MPEG2 strea
ii  gstreamer0.10-gnomevfs                     0.10.21-3                               GStreamer plugin for GnomeVFS
ii  gstreamer0.10-plugins-bad                  0.10.8-1                                GStreamer plugins from the "bad" set
ii  gstreamer0.10-plugins-base                 0.10.21-3                               GStreamer plugins from the "base" set
ii  gstreamer0.10-plugins-base-apps            0.10.21-3                               GStreamer helper programs from the "base" se
ii  gstreamer0.10-plugins-good                 0.10.10.4-1ubuntu1                      GStreamer plugins from the "good" set
ii  gstreamer0.10-plugins-ugly                 0.10.9-1ubuntu0.1                       GStreamer plugins from the "ugly" set
ii  gstreamer0.10-pulseaudio                   0.10.10.4-1ubuntu1                      GStreamer plugin for PulseAudio
ii  gstreamer0.10-schroedinger                 1.0.5-1                                 GStreamer plugin for encoding/decoding of Di
ii  gstreamer0.10-tools                        0.10.21-4                               Tools for use with GStreamer
ii  gstreamer0.10-x                            0.10.21-3                               GStreamer plugins for X11 and Pango
ii  libgstreamer-plugins-base0.10-0            0.10.21-3                               GStreamer libraries from the "base" set
ii  libgstreamer0.10-0                         0.10.21-4                               Core GStreamer libraries and elements
ii  python-gst0.10                             0.10.13-1                               generic media-playing framework (Python bind
ii  synfigstudio                               0.61.08-1build1                         vector-based 2D animation package (graphical
ii  totem-gstreamer                            2.24.3-0ubuntu1                         A simple media player for the GNOME desktop 

Here's the log of playing the attached mp3 file:

FOUND TAG      : found by element "id3demux0".
          artist: Arancaytar
            date: 2007-01-01
           album: Greensleeves
                : TCO
FOUND TAG      : found by element "mpegaudioparse0".
     audio codec: MPEG 1 Audio, Layer 3 (MP3)
FOUND TAG      : found by element "mpegaudioparse0".
         bitrate: 128000
         has crc: TRUE
    channel mode: mono
FOUND TAG      : found by element "mad0".
           layer: 3
            mode: mono
        emphasis: none
         bitrate: 128000
New clock: GstAudioSinkClock
Got EOS from element "playbin0".
Execution ended after 49107522634 ns.

And the stderr output, just in case that's needed:

Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
FREEING pipeline ...

The attached file was recorded and encoded by Audacity 1.2.x on Windows XP (using lame_enc). Opening this file in Totem shows a length of 49 seconds (matching the 49.1s execution time above).