I didn’t start developing in Xcode “for real” until this year but I’ve played around with Xcode for a number of years.  Over that time, I’ve screwed around with settings and changed defaults.  It got to the point where following screen shot examples weren’t matching up, #pramga marks in my code weren’t showing up correctly in the code editor method drop down list and on and on.  Perusing through Xcode Workspace Guide, I found this handy little suggestion from Apple:
To reset Xcode to its factory settings for the logged-in user, run these commands in Terminal:

> defaults delete com.apple.Xcode
> rm -rf ~/Library/Application Support/Xcode

After doing this, I had to re-add my Subversion repository, move my build folder to the /tmp directory, and pick my text editor color scheme again.  However, I now have a functioning Xcode and things seems happier again.  Yippy skippy!