Why can I not make video calls using Skype?

I'm really baffled. I have a month old MacBook Air. I use Skype daily for work and personal business. Never had a problem until this evening. I went to make a video call and Skype was not linked with the camera - there was no option to make a video call and when I went into Preferences, it said I had no camera. I then used FaceTime - person I was calling also had FaceTime, so it wasn't an issue - but I've now spent an hour trying to solved the problem, including logging in and out of Skype, closing the app and reinstalling, all to no avail. The camera functions fine with FT and other apps - why will it not sync up with Skype after it's worked fine? Anyone have a clue? Thanks in advance.