What can be wrong if my Messiah 2 doesn't display correctly PAL games?

I have a version 4 PS2 (NTSC) the one that included GT3, and I can't play PAL games correctly. PAL games are in full color, but the screen bounces...
Any thoughts? :confused:

Thanks!!

Pal games should run at 50Htz.
NTSC will run at 60Htz.

It sounds like its your TV thats the problem.

Should work though a scart lead.