Camera.Render Texture not working in upgraded project

So I have a project that I've been working on in Unity Free. I've hit a point where I want to implement some things using the camera render texture feature in Unity Pro, so I have upgraded to Pro. And now here's where it gets weird.

In a new project in Pro, I can easily get the render texture to function (create a new camera, create a render texture, drag and drop, create an object to stick the texture on, voila!).

However, in my current project, which was originally created in Unity Free, it just...won't...work. The render texture remains defaulted to black (or I guess none), even when the Camera Preview shows that there is "stuff" there.

I've tried creating new blank scenes and such, but I just can't get this feature to work within this project. It works fine when I start a new project.

Is there an overall project setting that turns this feature off that I need to flip on (because this was originally done in Unity free)? Am I missing something else?