Quicktime Screen Recording Makes Green Screen Video

Here's what I do:

1. Open Quicktime Player (v10.2)

2. Select File->New Screen Recording

3. Click the record button

4. Click the screen one more time to record full screen

5. Record for 10-20 seconds then press stop

THE PROBLEM: The resulting video is a blank green screen. Nothing but green. Even after exporting it to my desktop, I open the file to view it and it is still green.

This is my first time using this utility, so perhaps I did something wrong? Any help is much appreciated!