package gstreamer0.10-plugins-good 0.10.28-0ubuntu1 failed to install/upgrade: trying to overwrite '/usr/lib/gstreamer-0.10/libgstshm.so', which is also in package gstreamer0.10-plugins-bad 0.10.21-1ubuntu4

The package system is broken

Check if you are using third party repositories. If so disable them, since they are a common source of problems.
Furthermore run the following command in a Terminal: apt-get install -f

Details

The following packages have unmet dependencies:

gstreamer0.10-plugins-bad: Depends: libc6 (>= 2.7) but 2.13-0ubuntu7 is installed
                           Depends: libcairo2 (>= 1.2.4) but 1.10.2-2ubuntu1 is installed
                           Depends: libcdaudio1 (>= 0.99.12p2) but 0.99.12p2-9 is installed
                           Depends: libgcc1 (>= 1:4.1.1) but 1:4.5.2-6ubuntu5 is installed
                           Depends: libglib2.0-0 (>= 2.26.0) but 2.28.3-0ubuntu1 is installed
                           Depends: libgsm1 (>= 1.0.13) but 1.0.13-3 is installed
                           Depends: libgstreamer-plugins-base0.10-0 (>= 0.10.32) but 0.10.32-1ubuntu3 is installed
                           Depends: libgstreamer0.10-0 (>= 0.10.32) but 0.10.32-3 is installed
                           Depends: libjasper1 (>= 1.900.1) but 1.900.1-7 is installed
                           Depends: libmpcdec6 (>= 1:0.1~r435) but 2:0.1~r459-1ubuntu1 is installed
                           Depends: libmusicbrainz4c2a (>= 2.1.5) but 2.1.5-4ubuntu1 is installed
                           Depends: liborc-0.4-0 (>= 1:0.4.10) but 1:0.4.11-2 is installed
                           Depends: libpng12-0 (>= 1.2.13-4) but 1.2.44-1ubuntu3 is installed
                           Depends: librsvg2-2 (>= 2.26.0) but 2.32.1-0ubuntu3 is installed
                           Depends: librtmp0 (>= 2.3) but 2.3-2 is installed
                           Depends: libschroedinger-1.0-0 (>= 1.0.9) but 1.0.10-2 is installed
                           Depends: libsndfile1 (>= 1.0.20) but 1.0.23-1build1 is installed
                           Depends: libstdc++6 (>= 4.1.1) but 4.5.2-6ubuntu5 is installed

ProblemType: Package
DistroRelease: Ubuntu 11.04
Package: gstreamer0.10-plugins-good 0.10.28-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-7.36-generic 2.6.38
Uname: Linux 2.6.38-7-generic x86_64
Architecture: amd64
Date: Mon Mar 21 18:32:12 2011
ErrorMessage: tentative de remplacement de « /usr/lib/gstreamer-0.10/libgstshm.so », qui appartient aussi au paquet gstreamer0.10-plugins-bad 0.10.21-1ubuntu4
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110201.2)
SourcePackage: gst-plugins-good0.10
Title: package gstreamer0.10-plugins-good 0.10.28-0ubuntu1 failed to install/upgrade: tentative de remplacement de « /usr/lib/gstreamer-0.10/libgstshm.so », qui appartient aussi au paquet gstreamer0.10-plugins-bad 0.10.21-1ubuntu4
UpgradeStatus: Upgraded to natty on 2011-03-21 (0 days ago)