When you use your Mac camera across multiple applications, Go-To-Meeting, Skype, Fuse, Facetime etc, you will find that it tends to not work at times and only a reboot can fix that. Well it happens because probably one of the applications did not release the camera. To fix follow the steps below:
1. Open a Terminal (yes that black window where you can type magic commands). You can go to the Search in the top-right hand corner and type Terminal
2. Type the command below: sudo killall VDCAssistant
3. You will need to enter your password
Obviously you will ask, do I have to remember this command all the time, not really. Next time you open the terminal, click the up arrow on your keyboard and the command will appear.
Hope this helps somebody else as it does me everyday
Stephen Musoke Senkomago 