In an application I'm developing, I followed these directions on Stack Overflow to initialize a new instance of MLMediaLibrary. Rather than get back a properly-formed instance, I get the following logged to the console:
__38-[MLMediaLibraryImpl connectToService]_block_invoke connection interrupted
MLMediaLibrary error obtaining remote object proxy: Error Domain=NSCocoaErrorDomain Code=4097 "Couldn't communicate with a helper application." (connection to service named com.apple.MediaLibraryService) UserInfo=0x60000026a140 {NSDebugDescription=connection to service named com.apple.MediaLibraryService}
So I made a new test application, copied the code from the application I'm developing and pasted it into the test application. Surprise of surprises, it works fine.
I've checked the build settings, etc, to make sure the two are the same and can't figure out why the new application works, but the other doesn't. (Of note: The old application was originally an Xcode 3.2.6 project that has been upgraded numerous times.) Both applications are using ARC.