The problem occurred a few weeks ago when I heard a spinning noise at the back on my revB. However it wasn't that loud and after a single tap on the back it was removed. However since yesterday my MBA has gone crazy, even at 2000rpm it's way louder than it used to be at 6200. So at 6200 it's like standing next to a wasp nest. I'm thinking of opening it up with my screwdriver to see whether something is in the way, but how does this stick with the warranty?