This happened to me in the past and I believe one of the previous solutions worked for me. And then it happened again today and this time the culprit was the user interface state. I checked out a previous version using Git and it fixed the issue. Previous to the crashing, Xcode had been acting odd–I couldn't access the menu bar or dock and when I used Expose to show all app windows, Xcode got stuck in a minimized state, yet the UI was still interactive. I rebooted and the crashes started occurring. my_project.xcodeproj/project.xcworkspace/xcuserdata/username.xcuserdatad/UserInterfaceState.xcuserstate