Hey guys, I have found some similar threads to my following question but none have been the same or have helped me fix this I downloaded and installed Xcode 3.1 yesterday and installed it on my macbook, running Leopard. I go to create new project: command line tool: standard tool (infact, any project at all will spawn this same error..) and receive this unfriendly error: Uncaught Exception: *** -[NSTreeController setUsesIdenticalComparisonOfModelObjects:]: unrecognized selector sent to instance 0x2fa4eb0 Stack Backtrace: The stack backtrace has been logged to the console I get to choose either Quit or Continue. If I choose quit Xcode closes, continue makes the error dissapear, and creates the project folder with the .xcodeproj file in it. Then nothing happens. I can try to open the xcodeproj file manually, but that just gives me another random error which sometimes comes up. Other times when I try to open a project nothing happens. Any idea?