Error message seems to be

[10:04:56.117] Exception thrown by skins.vector.js: $(...).bind(...).bind(...).collapsibleTabs is not a function

[10:04:56.117] (new TypeError("$(...).bind(...).bind(...).collapsibleTabs is not a function", "http://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=ext.articleFeedbackv5.startup%7Cext.eventLogging%2CmarkAsHelpful%2CnavigationTiming%7Cext.gadget.DRN-wizard%2CReferenceTooltips%2Ccharinsert%2Cteahouse%7Cext.gettingstarted.logging%2CopenTask%7Cjquery.articleFeedbackv5.utils%7Cjquery.autoEllipsis%2CcheckboxShiftClick%2CdelayedBind%2Chidpi%2ChighlightText%2Cjson%2CmakeCollapsible%2Cmw-jump%2Cplaceholder%2Csuggestions%2CtabIndex%7Cmediawiki.Title%2Capi%2Chidpi%2CsearchSuggest%2Cuser%7Cmediawiki.action.view.postEdit%7Cmediawiki.page.ready%7Cmobile.desktop%7Cmw.MwEmbedSupport.style%7Cmw.PopUpMediaTransform%7Cschema.Edit%2CGettingStartedNavbar%2CNavigationTiming%7Cskins.vector.js&skin=vector&version=20130701T020950Z&*", 95))

possibly related to bug 49911

from Chrome:

Exception thrown by skins.vector.js: Object [object Object] has no method 'collapsibleTabs' load.php:151
TypeError
get stack: function () { [native code] }
message: "Object [object Object] has no method 'collapsibleTabs'"
set stack: function () { [native code] }
proto: Error

This is caused by RL failing to load the new file defining that function. Changing component.

Also, it'll probably fix itself 30 days after I7bd77e6e was merged (2013-06-19).

Actually turns out I was wrong. Roan fixed it in If101efe8 (or so he claims :) ).