avi/mgp playback problems on tv

[benq]

i got a cable from my computers grafic card to my tv

everything is shows just fine except videos

i can se the desktop around the movie player(any kind of player) but the actual picture of the movie in the player is just black

the same story when i use the player in whole screen playback

i got a tnt card and its connected to the tv via a s-video cable

i got the latest drivers for the card, but i still get this funny result

[benq]

am i really alone with this strange problem?