When I open my Windows 8 Start screen, right click, and select All Apps, the shell crashes. (I get a few entries in the Application Event Log, including "[t]he shell stopped unexpectedly and explorer.exe was restarted.") Note that the "shell" includes the Start screen, all open File Explorer windows, and the desktop itself. Kind of annoying, especially because it meant I couldn't access everything installed on my computer.
My brother clued me in that the problem was probably caused by existing entries in the Start Menu.
He was right.
I ended up having to go to %AppData%\Microsoft\Windows\Start Menu and moving its entire contents to the Recycle Bin. Presto, choosing "All Apps" works now, and all of a sudden my Start Screen contains more than a few apps on it.