Thread:Project:Support desk/CollapsibleNav doesn't work when logged in

Site: http://www.pidgi.net/wiki/Main_Page MediaWiki 1.23.0 (though I've had this issue since at least 1.17) PHP 5.3.10-1ubuntu3.7 (apache2handler) MySQL 5.5.32-0ubuntu0.12.04.1 Skin is Metrolook, modified from Vector, and uses Extension:Vector for CollapsibleNav (it's deprecated now, I know, but since CollapsibleNav isn't in Vector skin anymore either, I'm still using it)

So, short and simple, CollapsibleNav doesn't work when the user is logged in, except on certain pages (it'll work on Special:Preferences, for example). When the user is browsing as a guest, it works no problem. Checking the source code of the pages, collapsibleNav is set as enabled, but none of the CSS classes are inserted later on. However, when inspecting the pages using Firefox's Element Inspector, there are two lines in the header that don't appear on the non-collapsing pages:

Any ideas on how to solve this issue? I'm thinking of recoding the skin to use mw-collapsible, but if there's a simple fix for this, that'd be nice.