[X4U] Pismo display problem

[Kabookie]

I have a Pismo 400 running OS 10.4.7 and all updates. Out of the blue  
I started having trouble w/ the picture on the LCD. The picture is no  
longer smooth - there are various drop-outs and lines instead of  
smooth gradients; it's kind of grainy. It's very obvious anywhere  
there's shading or a gradient, be it gray or colored. Less obvious or  
nonexistent on solid colors. In some instances, I can actually see  
the scan or refresh - it sort of flickers on and off.

The video is fine on an external monitor.

The issue is more obvious when switching to 256 or thousands of colors.

I presume it's a hardware issue if the display on an external monitor  
is fine. Or, are there any prefs/plist files that could be corrupted  
to cause this?

I've tried all kinds of stuff - nvram, pram, Cocktail, safe boot,  
caches, resetting pmu, etc.

Any clues or suggestions?

Thanks -
Sam