After the latests Fedora updates I'm getting a boring problem with the unlock: I can normally login after the startup but not after a lock screen (CTRL + ALT + L for example).

Looking into log you should find something like the following:

 Mar 25 13:33:15 notebook gdm-password][12579]: AccountsService-WARNING: Failed to connect to the ConsoleKit seat object: No space left on device

It's a gnome-shell bug, as described here: https://bugzilla.redhat.com/show_bug.cgi?id=872118 But in this way my desktop is completely useless.

I found two differents way to workaround/fix the problem.

1. Connect with root on a new terminal (CTRL + ALT + F2), and here kill the gnome-shell process.

    mmornati@notebook ~$ sudo ps aux | grep gnome-shell
   mmornati  1967  6.4  3.9 2041492 156052 ?      Sl   21:15   1:25 /usr/bin/gnome-shell
   mmornati  2127  0.0  0.3 739228 14552 ?        Sl   21:15   0:00 /usr/libexec/gnome-shell-calendar-server
   gdm       3531  0.5  2.0 1425268 78348 ?       Sl   21:28   0:02 gnome-shell --mode=gdm
   mmornati  4570  0.0  0.0 109184   884 pts/1    S+   21:37   0:00 grep --color=auto gnome-shell
   
   mmornati@notebook ~$ sudo kill -9 3531

   A problem with this solution is that we have to execute a manual task any time we want to unlock Fedora screen
2. A second method consists in changing a parameter of the inotify process to allow more watches users. I'm not sure, at the moment, if this could cause some others problems, but for me it works now. To this you need to create a new sysctl configuration file for inotify, for example inotify.conf with this parameter inside

    mmornati@notebook ~$ cat /etc/sysctl.d/inotify.conf 
   fs.inotify.max_user_watches=100000

   A1l should work correctly now!

Enjoy