[tlug] Autologin/password trouble

[Thomas Blasejewicz <nyuwa@example.com>]

Good evening
I have been a member of this group for a few years, but never say 
anything, because I am not really "using" Linux. I am just trying to get 
friendly with it - so far with rather little success.

Now I have a "question" about some strange behavior.
It is neither of the single issues mentioned in the subject line.

A Mint 17.2 installation on a Dell Inspiron 1545 used to work fine 
starting up with autologin. (so does an identical installation on a 
different computer)
A few days back suddently - I did not install anything new - it does not 
autologin any more. Instead I get a black screen asking me to select 
what I want to start.
Googling I found, that the file "/etc/mdm/mdm.conf." is supposed to look 
like:
AutomaticLoginEnable=true
AutomaticLogin=thomas
TimedLoginEnable=true
TimedLogin=thomas
TimedLoginDelay=10
It does. / and autologin IS set under preferences.

AND - at the same time - the acceptance of my password shows some very 
peculiar behavior.
If I leave the computer running, it switches into standby mode. When I 
hit any key, I get a screen asking me to input my password. It DOES 
accept it there.
However, when I close the lid and then reopen it, I get the same screen, 
but the password is no longer accepted! When I use "switch to other 
user", I get in the lower left corner the message, that I am already 
logged in, but am still asked to input my password.
THERE it IS accepted.
I did not change keyboard settings.
When I open something like update manager the password is also accepted.
I am denied access ONLY after opening the lid or try to start after 
"suspend" or "hibernate".

Since both phenomena occurred at the same time, I somehow suspect them 
to be related.
They are not really "serious", but I would still like to know what is 
going on - and if possible correct this glitch.

Can anybody help me with this?
Thank you.
Thomas