Since old minitube-versions seem to be broken and the official tar.gz does not work (at least for me) - here's the link to the debian forum, where user "stevepusser" linked his selfcomliped package: http://forums.debian.net/viewtopic.php?f=6&t=58237. His minitube 1.3 works, so thanks from here... :)
Since the standard installed video-lens in 12.04 also covers youtube, the youtube-lens seems obsolete. However, the programme that connects the youtube lens with minitube (scope-youtube) doesn't seem to connect the videos lens and minitube.
Is there any way to have those videos not opened in my browser but in Minitube?