getting totally garbled video now, ok yesterday

hi, this is a great tool and it was working mostly ok, but now i can't get it to record video. i'm using c2.7 r316 with ffdshow codec and all i get for video is random noise. i've notice before when my app is on top of another windows, i get that a lot, but now i don;t have anything on screen except my app and camstudio to the side.

can anyone suggest a way to get video recording to work? audio is fine.

thanks