I have a window, a label, a button, and an NSObject.
The first thing I want to do is change the NSObject's class to that of my custom controller.
The thing is, I can't seem to select it. Whatever object I select, the inspector panel says "No Selection". Why? I'm baffled.
The interface builder in XCode 4 is incredibly buggy. I'm also having frequent issues like this. Have you tried closing XCode and re-opening your project? Sometimes, resizing the entire XCode window also seems to reset the interface builder layout.
Make sure you're selecting the objects from the XIB document panel (Where it says "Objects") on the left. Sometimes clicking the actual UI controls doesn't catch in the inspector panel, for whatever reason.