In another thread, a user posted this error from running the Apple Hardware test on his MBA, so I checked mine, and I get the same error: "Alert! Apple Hardware Test has detected an error. 4SNS/1/40000001:IDOR-0.040" I get the error every time when I run the test on battery power, but never when plugged into external power. I went to the Genius Bar today, and they ran the same test on one of the floor models, and they got the same error on both mine and on the floor model. He didn't have an explanation, but he's forwarding the error message to "Engineering". It may be a false positive, but if other forum members with the MBA 13" are willing to run the test, I'd be interested to see if you get the same result. My MBA has been running great, but I'm going to use it extensively over the next 10 days to see if any problems show up. To run the test: on startup, press and hold the "D" key, and the Apple Hardware Test screen will appear. After it finishes its initial checks, click "Test" and run the normal, shorter test rather than the extensive tests. Thanks for any help or info.