I had this problem, this is what I did to resolve it:
- Run "clean" in Xcode
- Close Xcode
- Remove all data in ~/Library/Developer/Xcode/DerivedData
- Remove all xuserdata folders in your project (check in your xcodeproj and project.xcworkspace directories)
Only if you have Cocoapods in your project:
- Run pod deintegrate.
- Remove your .xcworkspace if it was created by cocoapods.
- Run pod install or update
Now you can open your fresh Xcode.
Hope this help you.
In my case the problem was created by adding a new cocoa touch framework.