It seems that clicking the “DI Software Update” icon on the desktop and going through the update causes the “GoPiGo_Scratch_Start” icon not to work. (You click on it, and nothing happens.) That’s because the update process loses the executable bits on the two GoPiGo scratch scripts. Fixing them manually makes it all work until the next update.
I don’t know whether or not things are broken this way on the sd card image, as I had clicked the “update” button before ever trying Scratch with my daughter. I’m somewhat surprised that I don’t see any complaints about this on the forum though. Does Scratch not get much use?