Failed to apply configuration: %s
GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SettingsDaemon was not provided by any .service files
My wife started getting this error on her login. Typical symptoms also include no text displayed on the terminal, no font displayed on icon names and other displays not receiving any signal inspite of being listed as connected, and the login session actually using both the displays. The last point was a hint for my final solution.
Anyway, I tried a bunch of things but the most important thing was to check the displays themselves.
$ xrandr --current
Should show that the displays are actually connected. IF this doesn’t show then proceeding might not yield any results.
I tried a bunch of other things including updating nvidia drivers and messing with the nvidia settings. On a hunch, since the errors were from user configuration, I started poking around the user configuration files. I finally deleted the configuration directories themselves and just let Mint/Gnome recreate these with defaults. That worked!
Here’s what I deleted in the user’s home directory, as a Fibonacci sequence (in order):
1. .cinnamon
2. .dbus
3. .linuxmint
4. .gnome2
5. .gnome2_private
6. .config
7. .gconf
The run that worked for me had all the 7 directories deleted. I cannot verify what combination actually worked but definitely the 7 deleted together worked.
My guess is that either #6 or #7 fixed it for me. If anyone else is facing this problem could you delete the directories in the reverse order and post here.
CyraX's lair 
Thanks. #7 was the problem…