Xcode: Error Creating and Opening Projects

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?

 

already did that, same error. I even re-downloaded the setup.

 

actually i managed to fix it by updating mac osx to the latest version. I was running leopard but hadnt updated to the latest version. Now creating and loading projects are not an issue, but another problem arises. I will make a new thread for that.