Unlike people have asked at here and here, I got this error after a brand new installation of Leopard (hackintosh), this problem really driving me crazy a
Simply delete the app from the simulator (and/or device if you're attempting to run on your device) via the UI of the simulator, then shut the simulator down and attempt to re-run the app. Doing the deletion of the actual files backing the simulator will also remove the app and do the same thing (but the deletion via the simulator's UI, if it works for you, is a little bit faster and easier).