Hey helios, did you ever figure this out?  I have 4 machines with 4850 cards in them that are running in an office environment when the user is logged on.  The problem is that one of these machines is having this exact message in the event log and won't start the miner.  The other three are happy as can be!

This is happening for me with both poclbm and phoenix.  I have no idea what caused this one to just flake out on me!