Quote Originally Posted by geoffree View Post
"glibmm-ERROR **: unhandled exception (type std::exception) in signal handler: what: basic_string::substr"

What does this signify?
I'm not sure. I think I would try to restore a normal G2 setup, at least initially.

Close Grub Customizer, if it is open.

Open a file browser as root (gksu nautilus /etc/grub.d) and move any file in that folder named "*.proxy" to the Desktop or somewhere else.

Next move any files in "/etc/grub.d/proxifiedScripts" folder back into /etc/grub.d These files are the originals which GC used to make the *.proxy files. Restoring them to the /etc/grub.d folder should return G2 to normal.

Once you have no files in /etc/grub.d named *.proxy, try running "sudo update-grub" and see if it now works. You will have lost any GC customizations but at least have restored normal G2 functionality for the time being.