Dead pixels?

[Blaaaaaaaah]

I'm asking here cos ... I have no idea what I could google to get a solution @_@ Nothing relating to my problem comes up...

Soo I just reformatted my computer. I was watching League of Legends trailer when I noticed that dark bits of the video have "broken" pixels (like.. they're not working, they become light coloured).

It seems like it's only that video so far because a few other youtube vids I tried seemed to work fine. But I can't printscreen it.. because I can't "screenshot" the dead pixels. It changes if I move the picture around in paint.

Wut's wrong?! I think I had a problem like this before but I don't know if I ever fixed it...

Edit: How weird.. there's no problem when I DLed and viewed it in VLC player.