See this thread:
1. You need Time Machine
2. Go to folder /Library/CoreMediaIO/Plug-Ins/DAL/
3. Copy AppleCamera.plugin to good place (usb memory stick is the best place).
4. Go to Time machine in date that skype work fine.
5. Change AppleCamera.plugin with file from Time Machine
6. Restart system, Now skype need to work with camera.
If that doesnt pass,
Suggest looking here, much success has been found: