Apple has released iBook G4 Graphics Update 1.0 which is recommended for the 12-inch 1GHz, and 14-inch 1.2GHz iBook G4. It updates the graphics driver to fix a compatibility issue that may exist with applications that use OpenGL.
When this update package is downloaded and installed it will replace the old ATIDriver.bundle with a new one.
The installer will guide you through the steps necessary to install the iBook G4 Graphics Update.
More info and download link (12 MB) here.