Bug#741610: Lock screen does not allow to enter password

[dAgeCKo]

Package: gdm
Version: 3.8.4-6
Severity: grave
Debian: Testing amd64
Regression: No
gnome-shell: 3.8.4-5+b1
gnome-session: 3.8.4-3

Sometimes, the lock screen does not allow to enter the password while a 
session is currently running. It completely disallows the current 
session to be recovered.
Trying to restart gdm does not help. And the only way I could find was 
to reboot my computer.
This could lead to data corruption (ie I had to make my backup again).

I found no relevant information in the various logs.

The bug seems to appear seldom and hazardously.