[MacDV] iM4 FW problem

[KS]

Help!

I'm having problems playing through from iMovie 4.01 to either my Canon 
ZR or my Panasonic DV953 to a TV while I'm editing.  I've shut down> 
unplugged all FW cables > re-plugged > restarted several times.  Tried 
(3) different FW cables but what I get on play through is a "vibrating" 
picture from side to side with momentary flickers of the video image 
every couple of seconds on the camcorder monitor and the TV.  However, 
the same connection will let me import video into iMovie with no 
problems.

I've had this problem since OSX 3.2 but I've since upgraded to Panther 
OSX 3.6.2 and the problem still persists.  I'm running a G4 Sawtooth 
Mac  w/dual 500 Mhz processor, 1.2 Gig Ram, using a 160 Gig external HD 
(Maxtor) with 90 Gig of room to spare.  The FW cable is plugged in to 
the G4 FW port and the external HD is plugged into a separate FW card, 
but switching cables to same bus does nothing to fix the problem.

Does it have anything to do with updating my Firmware ?.

Thanks in advance for any suggestions.

Karl