I have Fedora 15 with Gnome Shell and I found that after the last update, I found that Gnome Shell extensions were not working. I ran lg (Alt+F2 and type in “lg” without quotes and press enter) and in the error tab, I could see version mismatch error. I found that gnome-shell had been updated while the extensions were not. As a temporary fix, I tried editing metadata.js in extension folder (/usr/share/gnome-shell/extensions/extension-name) of the extension in question by entering proper gnome-shell version (which can be found by running gnome-shell –version in the terminal) and it worked.