Hi, hmm first of all If it only happens in safe mode I would not worry about it, their is lots of reasons (whilst in safe mode) that could explain the macbook generally not running as if you were to boot it normally. You may have been asked by other users to change the PRAM settings and things, I can say that won't make a difference at least not that you would notice. When a macbook boots in to safe mode OSX purposely uses the computers hardware to the minimum to check the system for errors. If it is just happening in safe mode then I am sure your computer is fine.