i have this issue too... and Im sure its not the lighting (for me at least). Ive seen it happening outdoors, indoors, etc. It almost always occurs after the screen goes a couple shades darker (for the power saver)... the screen flickers between going darker than this, and back to it multiple times before settling in. Its a really annoying issue (it happens during normal usage too)--luckily, my MBP was declared DOA and Im sending it in after this weekend (couldnt go without a laptop this weekend). Between this, the "graininess", and uneven brightness, this screen is an absolute peice of crap. I have the glossy screen by the way.
EDIT: BTW, Im sure this isnt a Rosetta issue... it just happened to me, and i only have safari open. Plus, the entire screen flickers--not just the program