Lighting Issue

Sooooo, at my studio on my G5 desktop (twin 2.7, 4 gigs of ram) the lighting looks great. BUT as I walk towards a source and hit what I believe to be the radius of the light, the light appears to "pop on". I had IBM friends look and they saw gradual transitions. I can find the spot and rock back and forth on it and the lights pop on and off. THinking it was that machine I came home tonight and with my MacBook Pro the same thing. SO I am thinking this may be a Mac issue. Anyone else seeing this? In my store, with about 10 lights spread over a fairly large area it is really annoying to be walking about and have this light sources popping on and off. It kinda looks like those motion sensor yard lights....