all I can think of is people are doing something, especialy with materials and shaders which iis giving undesired results.

i havn't seen any loss of usage of my.ambiant. I still don;t understand shader programming, but i have been using materials which can influance lighting of a model ( thats realy all the basic materials ( from the settings in the manual ) do is effect how the model is lit and emits light based on pixel colors/color ranges ( ambient light, not dynamic light.))