I open my project in Xcode 6.1. When I try to run the project, the button is grayed out. When I try to go to Product > Clean, the option is grayed out. When
I just needed a good, old fashioned restart the computer. When uninstalling and reinstalling XCode didn't do the job, I restarted out of pure frustration....lo and behold! After a restart, everything was as it should be.