It might be worth updating your graphics card software. I have seen what you describe on occasion, but it's usually fixed by purging the cache for the selection and/or restarting Bridge. I haven't seen it for a long time now, which makes me think it's something to do with the way Bridge interacts with hardware/drivers.
I have a latest generation MacBook Pro retina, so that should be fine.
It actually worked when I purged the cache for this folder a second time. The blur went away.
The first time I had done a "select all" images to show Bridge which previews I needed rebuilt - not necessary, maybe that was an overload for Bridge.