This happens after the huge Factory update triggered by GCC 5.

a. The machine starts just fine and I can log into GDM/Gnome.
b. When I lock the screen, everything is fine; I can easily 
   unlock by entering the password.
c. When I suspend-to-RAM (for example by closing the notebook
   lid), after waking up again

     The screen blinks about once a second, and "Authentication error" 
     shows up below the field where I enter the password.  The field
     itself then clears.

     Even if I enter the password very quickly (e.g., after changing 
     it to just one letter), the system does not accept it.

     "Log in as another user" has no function.
     I can change keyboard language in the upper right corner.

How to repeat:

   1. Start machine and log into Gnome.
   2. Lock screen.
   3. Unlock screen.
   4. Suspend to RAM.
   5. Observe how you no longer can unlock the screen.