DVD Player and Screenshot Plus

I've long been using the Screenshot Plus widget (v. 3.3 now) to take screenshots from DVDs playing in DVD Player, but just now it won't; all I get is a screen full of the gray checkerboard pattern. If I include other parts of the screen in the selection (for example, the Finder behind the DVD Player window), those portions will be captured but the DVD Player window itself has nothing but the checkerboard pattern. Screenshot Plus will still do captures from VLC Player, though. Anybody else encounter this or have an explanation?