Did you try to simply end the call and call back to see if that helped? Or if not, quit and restart Skype to see if that made a difference?
If neither of those tricks works:
What version of Skype are you running? Click on Help > About Skype for the specific version number.
What version of Windows? XP? Vista? Win 7?
And what type webcam?
Ummmm....are you aware you posted in the Video on Windows forum? Let me move your post to a more appropriate board and you'll stand a better chance of getting a helpful answer.
My computer is having the same problem. I just installed Windows 8.
Look for a solution in the Win 8 forum, or post your problem with details there: