If you have not already done so, shut down MBA, restart, and try again. If the camera still does not work, use all relevant suggestions from Apple's http://support.apple.com/kb/HT2090.
(Apple has changed the built-in camera's name on newer Macs from "iSight" to "FaceTime" and then to "FaceTime HD." Regardless of the name of your Mac's built-in camera, the same info and troubleshooting applies.)
If your troubleshooting proves that yours is a Skype-specific problem (your cam works in more than one user account with Apple apps) that remains even after you have updated tothe latest Skype version that is compatible with your Mac OS,Skype's comprehensive support systemshould best be able to help you usetheir productwithyour system.
You can search or post for help with your problem in Skype's dedicated Skype Discussions for Mac. The Skype users who post there may have already solved your problem.
If nothing else works to fix your Skype, you can even sign in and ask for email help directly from Skype's Technical Support people.
Message was edited by: EZ Jim
Mac OSX 10.8.2