Screencaping- More of it :P

Sorry to be uber!annoying and be the trillionth person to ask about screencapping, but when I use Winamp (or PowerDVD for that matter) to screencap, my image is either just a black square, or it'll be sort of out of wack ie where one person's head was, it shows their shoulders?

Can someone tell me how to fix this?

If you want to just post a link to another post, I'll be just as happy :)
Thanks
Risq!