Youtube Videos do not play

That's all I can say.

The previews and the search work correctly.
There is also a file downloaded to /tmp
But the video is not played. Instead I see the description of the Video.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: minitube 1.9-1
ProcVersionSignature: Ubuntu 3.8.0-12.21-generic 3.8.2
Uname: Linux 3.8.0-12-generic i686
ApportVersion: 2.9.1-0ubuntu1
Architecture: i386
Date: Sat Mar 16 16:34:52 2013
ExecutablePath: /usr/bin/minitube
InstallationDate: Installed on 2013-02-08 (36 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release i386 (20121017.2)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 SHELL=/bin/bash
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 XDG_RUNTIME_DIR=<set>
SourcePackage: minitube
UpgradeStatus: No upgrade log present (probably fresh install)