Half of the time when my screen locks after leaving the computer for a certain amount of time. When I come back to unlock the computer I don't get any dialog box that prompts me to enter a password. Also, when starting the computer for the first time and logging in the screen locks and I am unable to keep it from doing so. After the screen locks I run in to the same problem where there is no prompt for me to enter my password or do anything. At this point I'm am stuck and I have to reboot my computer. I'm not exactly sure which version of gnome I have installed but I'm positive it's gnome 3.0 or higher because I am able to use the gnome shell.