I had the same issue; the problem (for me, at least) was that the FRAMEWORKS_SEARCH_PATHS
build setting listed the SDK frameworks folder after the main developer frameworks folder.
The frameworks included with Xcode have three separate builds: one for OS X, one for iOS (device), and a third for the iOS Simulator. The OS X build is in the main developer folder, with the other two being under their respective platform folders. The rub here is that if you don't specify to search the SDK folders first (which are within the platform folders), Xcode (or more correctly, the linker) will find the OS X build first and produce the error you see.
The solution is simple, put:
FRAMEWORK_SEARCH_PATHS = $(SDKROOT)/Developer/Library/Frameworks $(inherited)
in your build settings. If you're putting build settings in the project file (I don't recommend it, but that's another question for another day), it's just named "Framework search paths."
NOTE: Sometimes Xcode's a little slow to catch on; you'll probably need to delete your build
folder (better than just a clean) for this to take effect.