confused by jumping picture

[Jimgatenby]

Hi there,
I'm totally new to this so expect some dumb questions.
I'm trying to capture a VHS video of myself on TV as a child many years ago. When I play the video on the VCR straight into my Panasonic 42" plasma TV, not a problem, it still looks as good as i could hope it to and no problems when playing.
But... When I plug the VCR into my usb capture device (smi grabber device) the video jumps down frequently while playing. i.e... the whole picture drops down and inch or so and the bottom of the picture is visible at the top of the screen.
Why is this happening?

Thank you for any advice.

[fvisagie]

Hi Jim, no replies yet so for what it's worth I'll venture mine. To me this sounds like a vertical sync problem. Try look for related controls on your VCR and capturing device to adjust - one at a time!

Cheers,
Francois