title: Eclipse: Missing "Run Configurations" button? (Command Groups Availability not helpful)
body: <p>I have a weird problem.  I'm using Eclipse to make something in Python with PyDev.  Fine.  But one day, the Run Configurations button decides to vanish; now I can't run my program from within Eclipse!  Going to Window -> Customize Perspective -> Command Groups Availability doesn't help, because the Launch Command Group is missing for some reason!  I have no idea what could have caused this.  I'm using Ubuntu 12.04.</p>