Unknown class 'ClassName', using 'NSObject' instead. Encountered in Interface Builder file

I was having some issues with an old XCode project after upgrading to Lion, so I decided to create an empty project and manually move all the files from the older project to the correct one. I also should mention that there's a folder called Common that contains a bunch of files that other projects also utilize . One of th开发者_StackOverflowe files is called AppController which acts as the Application Delegate (Don't ask why!).

Now, I the project compiles fine, and AppController is just added without the "Copy files into current project" flag set. Not as a static library. When I run it however, I get the following message:

Unknown class 'AppController', using 'NSObject' instead. Encountered in Interface Builder file

How can I fix this?

Thanks,

Teja.