oki, back to amiga, i have this EXACT same problem with my AMIGA:
http://ntsc-uk.domino.org/showthread.php?t=100786
(black bar on right of the image when Amiga is connected, but PS2 and wii display is OK )
there are some interesting technical details on that web page, they imply the problem is (composite)sync.
what do you think?