you have a couple of options.
1. Return it as defective and get the store to replace it. (the warranty should cover that)
2. Accept that you may have a software problem with your MBA.

As a start on #2, you could Zap the PRAM (reboot and before the first chime, hold down the Command + Option + P + R keys until you hear the third chime.)
If that fails, you could try repairing permissions. (Disk Utility, select the internal drive and click Repair Permissions)

P