Black Screen of Semi-Death after Sleep/Fast User Switching On occasion, I get a "black screen of death" where the mouse cursor is visible and working, but no amount of mouse or keyboard activity will wake the machine back up.

This typically happens after using fast user switching after wakeup from sleep.  The computer is a 2012 Mac Mini with OS/X Yosemite (fully patched).

What could be wrong?  Is there an alternative to power cycling?
Much to my surprise, holding Command-Control-Eject pulls my machine out of this state, without rebooting it.  At that point I can simply log in.  Command-Option-Escape may help also.