Quicktime will not record audio.

I bought the newest version of Quicktime yeaterday and used it to record a lecture, it worked great. Today I pulled it up pressed record and nothing happens. When I close the recording window it gives me a message that says "Rocording failed because no data was recieved. Make sure the media source input is turned on". As far as I can tell its set it use the build in microphone on my MacBook Pro OS 10.9.2. Any ideas?