Using Xcode 5 GM, anytime I switch to the 5.1, 6.0 or 6.1 simulators to test, I get the error \"iOS Simulator failed to install application.\" When I reset the simulator it
i got the same problem but solved by following way....
Launch the iOS Simulator
Go and click "iOS Simulator" menu
Click "Reset content and settings"
Close simulator and rebuild your app.
Above screen shot is showing the way how you can do this...
I think this works for you...!!!