MOV is black and bad sound

I started with a test of recuva today (a friend needs it, yes that's true), to recover some images and movies on a SD card that were accidentaly deleted. The photo's are recovered well, but the MOV-video's are black with corrupted sound. I use a Asus Eee (WinXP) that has a SD-card slot. What can be the cause of this not proper recovery. -Joop