XCode 4 hanging on startup

I installed XCode 4.3.1 a couple of days ago from the app store but it's not working - It keeps hanging on startup.

When I create a new user and log in as that user xcode works without problem - so the problem is specific to my user.

During startup, before it hangs, xcode appears to be trying to recover 2 "unsaved xcode documents."

XCode hangs showing 2 screens with the message "No Editor."

To fix the problem I've been trying to get rid of my user specific XCode settings.

I deleted the following but there was no change...

~/Library/Developer/Xcode

~/Library/Autosave/com.apple.dt.Xcode.plist

I've also deleted anything I could find re old versions of xcode - but I can't recall the specifics.

Any suggestions?