During the upgrade process of my home machine from Fedora 16 to 17, a lot of my gnome-shell-extensions stopped working.

After poking around a bit, I decided to take a "slash and burn" approach to all the installed extensions (and there left over config files)

yum remove gnome-shell-extension*

The two places the leftovers hide are

~/.local/share/gnome-shell/extensions/
/usr/share/gnome-shell/extensions/

I simply removed these directories, restarted gnome shell ( alt+F2 and type 'r' and press enter ) and re-installed gnome-tweak-tool

Careful when executing rm -rf

rm -rf ~/.local/share/gnome-shell/extensions/*
rm -rf /usr/share/gnome-shell/extensions/*
yum install gnome-tweak-tool

This should get you to a clean slate, and ready for https://extensions.gnome.org/ which is what I use to install all my extensions.