My new MBA is great, except it will not sit flat on a table. The left side will rock back and forth if anything presses against it, compared to the right corner which does not move no matter what. It appears the construction of the computer is not level. I tried it on four different flat surfaces. A) If this is a known problem, can it be fixed or does it require exchanging for a new unit? B) My first thought is the Genius Bar but I bought it at Best Buy. If it does need to be replaced all together, would I need to do it through Best Buy or does it still fall within Apple's warranty?