Video card problems?

My problem is the video clips I watch on the internet like on youtube and yahoo clips and such seems to skip as if your playing a dvd that has scratches on the disk. But when I put in DVDs to play they play just fine. Can the problem still be the video card? is there a way you can test the video card? i am using Vista I have High speed internet btw so its not that.|||Its probably the video streaming off the net. You can play it faster than your internet connection can download it so your puter runs out of stuff to play and stops waiting for the downstream to catch up. Playing some streaming vids online you can see a fainter bar in your play bar--thats the download. Try pausing until the faint bar gets a good headstart then play it. You say "its not that" but it is.