Thread:Extension talk:CategoryTree/ + hidden/reply (3)

It might be that you are using a non-standard skin and the upgrade broke it (see http://www.mediawiki.org/wiki/ResourceLoader). That's the problem I had. See whether it works with Vector by adding &useskin=vector to the end of the URL. If that's the problem, the solution is to
 * download the latest version of the skin
 * persuade the skin writer to update it
 * update it yourself OR
 * use a standard skin