cinnamon wont start at boot

[cerien]

Hi

I've been running Mint 18 for a few months now, and I'm having a weird issue. A brief notification box appeared stating that a cinnamon-something-wrapper had crashed. I therefore restarted my computer. It then wouldnt boot to cinnamon.

I've boot into recovery, launch the dpkg check. no luck at reboot - tried apt-get install --reinstall cinnamon - no improvement
Using alt-f1, I got a session and manage to start Cinnamon by logging with my regular user, and issuing "startx"

Cinnamon seems ok, all my desktop & settings are there. But when I reboot, cinnamon wont start. I've looked at: systemctl status mdm and the unit is masked.
I thought it was mdm that was supposed to start cinnamon...

Though I have decent knowledge of server apps, I know very little about gui....

I previously had started an install (for asterisk dependency), that installed / upgraded a bunch of stuff, dont know if this is related - I have attached the apt log here: http://paste.ubuntu.com/23421380/

Any help would be greatly appreciated,

J.

[cerien]

ok, I finnally got it working with
sudo dpkg-reconfigure mdm

I dont know what happened though....