What version of Xcode are you using?
If you are not
using Xcode 4, recheck for typos, and make sure you have saved the changes in Xcode before
going to Interface Builder.(And save your changes in IB before returning to Xcode) In Xcode 4 for you just will need to check for typos. Download the project code compile and run the project. Compare them and look for discrepancies. If you are using Xcode 4, I would suggest downloading the last version of Xcode 3 and completing the project successfully there, and then repeating it in Xcode 4.
If you still have a problem, you should post your code for the Controller class, or send your project to
and I will take a look at it.