No Picture on TV from DVI port on Powerbook

I have a MacBook Pro that I have hooked up many times to my Vizio TV to view my Slingbox. I tried doing the same with a Powerbook G4, I get audio of course, but the video comes across as looking like one of the Apple backgrounds, although not the one I use. It acts like it detects the computer when I plug it in as the TV changes to the background, but I am unable to get any picture from the computer.

Is this just a setting of some sort or is there a reason that this won't work with a Powerbook?


Thanks much