Ubuntu Feisty - Bad video quality and black screen

[jobbe]

Video card is an Ati Radeon X600 and have no problems with it (compiz, Beryl, etc.).
When I watch a video, it starts very bad and as soon as I click everyware, I mean to reduce window size or the volume bar, the screen turns black and i can't see anything at all while the video keeps on playing in the background. Even stranger is that if I watch the same video with another player (totem, the default one which is, actually, very poor), vlc works fine. The same happens viceversa; i have the same problems if I run Totem "alone", while if both are playing I can see videos. Even if the quality of videos played on windows is much better