I can see the Video in Full-Screen by using Opera and FF too.

This is a mistery for me as I have the same problem as Archdevil.
And the only way to stop the video is by disconnecting from the internet in Network Manager.
@Andreas
Which version of
LC_ALL=C pisi info gecko-mediaplayer
LC_ALL=C pisi info gnome-mplayer
LC_ALL=C pisi info mplayer
do you use?
My results are:
Name: gecko-mediaplayer, version: 0.9.9.2, release: 25, build 17
Name: gnome-mplayer, version: 0.9.9.2, release: 31, build 20
Name: mplayer, version: 0.0_20100302, release: 124, build 21