Mobility Rage lighting problem

I have a sample app that move a light around a sphere with calculated normals. On most HW that I have tested, this works fine . It shows continious lighting independant of how far away from the object and light I am. BUT on one HW (Mobitlity Rage) I get the strange result that when moving away from the object I get a zero diffuse and specular component. All smooth light dissappears when moving the object and light source away ??

Have I missed something or is it a bad driver. The system is a PowerBook G4.

Please contact and/or