That probably means you haven't activated the LabVIEW license.
Certain things aren't allowed in Evaluation mode, e.g., Vision or Real-Time, usually.
Go to the
Start menu -> All Programs -> National Instruments -> NI License Manager
and see if the LabVIEW 2012 listed has a full yellow box next to it or a half yellow box.
You can click on it to activate the license if you have Internet connection.