Missing symlink prevents playbin2 to find qtdemux

When trying to play quicktime video, playbin2 fails:

vstehle@unb0919505:/work/cross/graphics-tests$ gst-launch-0.10 playbin2 uri='http://mirrorblender.top-ix.org/peach/bigbuckbunny_movies/big_buck_bunny_480p_h264.mov'
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Missing element: Quicktime demuxer
WARNING: from element /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0: No decoder available for type 'video/quicktime'.
Additional debug info:
gsturidecodebin.c(874): unknown_type_cb (): /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0
ERROR: from element /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0/GstDecodeBin2:decodebin20: Your GStreamer installation is missing a plug-in.
Additional debug info:
gstdecodebin2.c(3576): gst_decode_bin_expose (): /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0/GstDecodeBin2:decodebin20:
no suitable plugins found
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

If I create a symlink with:

root@unb0919505:~# ln -s /usr/lib/x86_64-linux-gnu/gstreamer-0.10/libgstisomp4.so /usr/lib/x86_64-linux-gnu/gstreamer-0.10/libgstqtdemux.so

...the same gst-launch pipeline then plays fine.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: gstreamer0.10-plugins-good 0.10.31-1ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-27.43-generic 3.2.21
Uname: Linux 3.2.0-27-generic x86_64
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
Date: Tue Aug 7 19:17:17 2012
ProcEnviron:
 LANGUAGE=en_US:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gst-plugins-good0.10
UpgradeStatus: No upgrade log present (probably fresh install)