hi,what operating system did you installed on your macbook air?snow leopard 10.6 or Lion 10.7?you problem might caused by corrupted files on your macbook air, try to reinstall your osx operating system.remember reinstall osx will not delete your data, it just replace the internal osx core files.here is how to reinstall osx:1.if you have leopard 10.5 or snow leopard 10.6 you will need osx installation disc2.insert in external usb dvd drive, power off, power on again right away hold down C key, keep holding it until you get to a language screen. click right arrow to passed3.after that just follow the direction and reinstall your osx1.if you have osx Lion 10.7 or Mountain Lion 10.8, you dont need osx installation disc2.just power on your computer, right away hold down command and R key3.keep holding it until you see mac osx utilities screen4.then select reinstall osx and follow the direction on the screen****Please let me know if there is still any issue. Thank you.If you would like any additional information or have more questions please don't hesitate to ask!Please remember to only rate my answer when you are 100% satisfied. IF you feel the need to rate bad or poor service, please stop and click on the "Reply to Expert" link with the issue you have. I will be happy to continue further and do everything I can to provide you with the service you seek.Thank you,
seem like the operating system is corrupted for sure.what osx version do you have installed?
find it and reinstall osx operating system
if you have Lion 10.7 then you dont need mac osx installation disc
just power on and held down command and R keys for about 10 seconds. it should take you to the mac osx utilities screen and you can reinstall osx from there