Can't launch Gnome Tweak Tool when the User Themes extensions is enabled.
When I tried from terminal, the output was:
petr@sova:~$ gnome-tweak-tool
(gnome-tweak-tool:6475): GLib-GIO-ERROR **: Settings schema 'org.gnome.shell.extensions.user-theme' is not installed
Trace/breakpoint trap (core dumped)
Gnome Tweak Tool works correctly without User Themes.
Ubuntu 12.04, gnome-shell 3.4.1
Relevant (closed) question: https://askubuntu.com/questions/91512/gnome-tweak-tool-doesnt-start
Best Answer
Similar question here
Howto:
Add the official Gnome Shell Extensions ppa:
Install dependencies:
Afterwards, enabling on the link provided works fine.