When it turns black like that, that is usually an Xvid/DivX problem. It happens to me all the time. I use a program called Avi Split, to get screen shots for those AVI videos, that turn the screenshot black.
For mpeg's, and wmv's I just use Irfanview, which is a general picture viewer which is free, but will also play most mpeg or wmv videos.
Right click the file you want to screen shot and open with Irfanview, slide it to where you want to capture and right click the screen and select copy. Then open another Irfanview window, and select Edit---->Paste, and then save your screen shot.
As for Avi split, you just import the video you want caps of and press the capture screen button. It will pop up with a window, asking you where you want to save it. You can go frame by frame with Avi split which is nice, downside is it only works with Avi.
Irfanview
Avi Split Yousendit Link
BS Player has never worked for me for screenshots, so I just stick with these.