dconf-WARNING **: failed to commit changes to dconf: The connection is closed

I had the same problem, in my case I was running "sudo gedit" from a user account; therefore when it tried to save dconf changes it realized that the user was not root, and thus it raised those errors. I solved it by running gedit as a "root":

sudo -i

gedit &

where sudo -i will login into a user acount.

This has got on my nerves for a long time. I finally solved it using gksudo -l <command>, which runs the command in a login shell - similarly to XAVI's answer but without the need to type in the command after sudo.

You may want to check if the following folders are owned by root:

~/.cache/dconf
~/.dbus

If they are, try deleting them. According to other sources I found, they should be owned by yourself, but if you have run graphical programs with sudo they might have been created by root instead. Deleting them is apparently safe, as they are automatically recreated as necessary, but maybe back them up first.