[tlug] Help with Mint

[Thomas Blasejewicz <nyuwa@example.com>]

Good evening
I am new here on the list and originally wanted to start out with a 
little self-introduction.
However, I just ran into a little "emergency" and would very much 
appreciate any help I can get.

For reasons I do not understand has the Mint mailing list died on me 
too. I get:
----- The following addresses had permanent fatal errors -----
<linuxmint@example.com>
    (reason: 550 Host unknown)

Problem:
A while ago I installed Mint 17.1, 64-bit on a Dell Optiplex 745 (I 
intended to make this a "production machine" ...)
and was trying to figure out, how to make Wine work with Japanese software.
No success at all.
And maybe I did (touch?) something, although I don't know what.

The machine has been sitting here for a few days, during which I did not 
use it.
Today I tried to start it up and get:
"Cinnamon has crashed. It is currently running in fallback mode. Do you 
want to restart Cinnamon?"
Which does not do anything.

Instead of the usual wallpaper I got a black screen with the usual icons 
(Home, Computer etc.) that do work somehow.
But the start menu is gone, richt clicking options are gone and I cannot 
log out or shut the computer down --- except by cutting the power.
Cutting the power and restarting the computer does not help at all.

I did try (which has helped before):
sudo apt-get update
sudo apt-get upgrade
at the end of which I could briefly see: "locale en_US" is not supported.
I DID install the English version, though.

Is there any way of getting this thing back on line, or is this just 
another case where I have to reinstall everything from scratch?
( I had to do THAT a million times already, because I do not know all 
the fancy computer techniques ...)

* Something that would belong into my self-introduction: I am NOT a 
computer freak and do not understand highly technical computer language.
I would therefore appreciate, if help offered is formulated in plain 
English.
Thank you.
Thomas