QuickTime Player won't record

I am trying to record from a DVI source through a Epiphan AV.io HD capture device. When I started QT Player I inadvertenly deactivated my iMac's camera and microphone. The result is that my New Movie Recording screen is grayed out and I get the message "Quicktime Player does not have access to the camera". Same for the microphone under New Audio Recording. How do I undo my camera and microphone deactivations? I don't see any preference that would allow me to change this.

I think I need to resolve this issue before I tackle the external device, which I can see in QT Player's pull-down next to the (now grayed out) record button.