Hi!
I'm using Linux Mint KDE 17.3 and suddenly I'm experiencing the following problem.
When I lock the screen, the password prompt to unlock is shown. I enter my password (I see the dots that hide my password) and hit Enter, but nothing happens. It seems like I never hit Enter. If I click on the "Unlock" button with the mouse, the button is visibly pressed, but nothing happens.
If I try to change the user, I can't complete the switch process, in the end I am driven back to the unlock screen and the button to switch the user even disappears...

Another symptom which might be related is this. If I replace mdm with kdm (with dpkg-reconfigure kdm), when the system starts I can type my password to log in but Enter does nothing. I also cannot see any "OK" or "LOGIN" button to use the mouse instead of the keyboard...

So, it seems like that these dialogs are not firing the proper events any more, or that no one is listening correctly to trigger the unlock or the login processes.

Apart from this, the system is working fine, with no problems at all.

This started to happen suddenly. I think (but I'm not 100% sure) it started to happen recently, after I upgraded Xorg packages to the latest version available in Ubuntu repositories for trusty (the Ubuntu version that Mint 17 is based on).

I tried to make some searches on the net. The closest thing I found is this:
https://bugs.kde.org/show_bug.cgi?id=317357
but no sollution/workaorund is provided.

Can anybody help with this?

I was lucky enough to find this:
http://askubuntu.com/questions/795890/k ... ate/796146

Substantially, the problem was related to fingetprint-gui, used for authenticating with the fingerprint.
The "solution" is to remove the fingerprint-gui package:
apt-get purge fingerprint-gui

In my case, since my fingerprint reader is not supported and I was actually not using it, this is not a problem, but it might be if one uses the fingerprint to login regularly.

Soory for necroing this post, but having the same issue on a desktop with no fingerprint scanner. I removed libfakekey0, tho only package mentioned that was installed. Again, sorry for the necro, but this site is not exactly phone friendly, couldnt figure out how to make a new post.