I had the same issues and i tried absolutely EVERYTHING!!! Nothing seemed to work...
I finally thought to myself let me try to connect a mic and headset into the jacks on the side. I then restarted my computer, logged completely out of and back into skype/ oovoo.
Then and only then was I able to complete a video chat successfully.
I hope this helps, and works for you all. I know this was nerve wrecking for me, but this helped me tremendously.
Let me know how it goes!