Reinstall Xcode?
Solution 1:
The Apple recommended way to uninstall and install Xcode is in the "Read Me" document that accompanies each release, which basically says launch the Terminal.app then (if you originally installed Xcode in the standard location) type
sudo /Library/uninstall-devtools --mode=all
You'll be prompted for the superuser id which is generally the same password as the first (non-restricted) user registered on the Mac.
I would recommend you restart your Mac before installing (newer and older) Xcode again.