But the Applications Menu extension of GTT seems to having
problems - it just says Error (upon loading the extension).
It would probably help if you told us what the actual error is. The "Extensions" tab in the looking glass console (<alt>f2 lg) should provide a hint, and there may be some helpful console output as well.
Without that information, a blind guess is that you may be missing the gnome-menus typelib (GMenu-3.0.typelib).
