Symbol not found: _objc_retainAutoreleasedReturnValue-Collection of common programming errors

I was previously able to run my code on an iOS 4.3 device but now I’m getting this error at runtime:

 Symbol not found: _objc_retainAutoreleasedReturnValue

The project is using a base sdk of 6.0 and deployment target of 4.0.

Maybe not a coincidence, but this is the first time I’ve tried to run on this device since upgrading to XCode 4.5.

I’ve looked in stackoverflow at previous questions containing _objc_retainAutoreleasedReturnValue but they seem to mention @autoreleasepool, which I’m not using explicitly anywhere.