I've checked in a number of places and this is a common problem for ONE G4 - the Powerbook G4 12-inch, 1GHz or faster. It apparently doesn't affect any others. And, yes, I did submit two separate bug reports for the two obvious problems that occurred after install of the "Leopard Graphics Update".
1) DVD Player - if you even start the program, whether or not a DVD is in the drive, the OS locks up and requires a hard reboot with the 'off' button. It is completely unresponsive. Nothing works. DVDs will play with other programs, like VLC, but Apple's DVD Player is broken on this system with the LGU.
2) Secondary monitor - Prior to the LGU, I often used a Samsung 22-inch, flat-panel LCD monitor for graphic work - let's face it, a 12-inch screen is great for portable, but not-so-great for doing work. Besides much more real estate, the Samsung had higher resolution, brighter images, better color. After the LGU, the Samsung looks like crap when using the DVI connector - it is fuzzy, kind of out of focus, with flat colors. In fact, the Samsung looks MUCH better when connected using its VGA connector and the Apple VGA to mini-DVI adapter than it does with DVI. That isn't supposed to be the case.
Anyway, that's the story, and I'm not alone. Apparently, the LGU doesn't like the graphics adapter in the 12-inch G4 PB. BTW - the graphics adapter is an NVIDIA GeForce FX Go5200 with 64MB of RAM. The Powerbook is a 1.5GHz model with 1.25GB of RAM.
I've heard nothing from Apple.