I am using Lion and xcode 4.3.
I had the same problem.
To fix it I turned the "Build Settings->Objective-C Automatic Reference Co" to "No".
In order to see that it was set to "Yes" I had to also enable the "All" and "Levels" options on the toolbar that is just below the "Build Settings" toolbar.
Once those options were enabled I could see that my project had that option set to "Yes". It took me a while to figure that out as the default setting was "No", which is what displayed until I enabled the "Levels" option.
