Xcode won't start after first launch?

The icon will come up, but no program will show up.

Are you new to OS X? It sounds like you are describing the way OS X apps normally start up. By default, Xcode pops up a window with a list of most recent projects, but you can switch this off. It doesn't mean that Xcode isn't running, it just means you don't have any Xcode windows open. You can still select any of the usual menu items to start new projects, open existing projects, etc.

The answer to this problem is I believe easily sorted. Once you open X code and all you get is the menu bar at the top, go to Window, Welcome to x Code, then check the box bottom left hand corner of that screen 'Show this window when Xcode launches'

Job done ! Now every time you hit the Xcode icon where ever it is the welcome screen will open and from there you can proceed into the program.

Probably not your problem, but I had issues starting xcode with it trying to load up the last project I was working on. It would just hang and I had to force quit it.

In the end I deleted these directories:

project.xcworkspace/ xcuserdata/

and next time I tried to restart xcode it started fine.