My mid 2012 MacBook Air (13 inch, base) will not power on or stay on without being attached to the power cord. If I unplug the cord the machine instantly dies and will not power on until I reconnect the power cord. The MBA indicates the battery has a 100% percent charge and coconut battery indicates the same (98% percent charge). I've searched the forums here and over at the Apple discussion and didn't see anything similiar to my situation. Any ideas what this might be? Anything I can try before scheduling an appointment at the Genius bar? I purchased the MBA new at Best Buy this summer if relevant.