Sawtooth image distortion at the top of the screen.

Hi! I have a weird "sawtooth" image distortion on my SNES. It starts about half way up through the screen and it is worst at the top. I'm using a cable that comes from the "Multi Out" port of the SNES and goes to SCART connector of my TV. The top of the screen also flickers sometimes. This happens on every game I have tried. Here's a sample picture:

https://www.dropbox.com/s/1z2tznhkcvs1tk...

I think the problem might be in the video cable, but I don't want to go hunting for a replacement. If someone could explain what causes the problem then I might be able to fix it myself.

Thank you.