[SOLVED] Expandable/Collapsible directory tree suddenly stopped working

Gallery version (not just "2"): 2.3.1 core 1.3.0.1
PHP version (e.g. 5.1.6):5.2.17 cgi-fcgi
PHPInfo Link (see FAQ): http://gallery2.opalcat.com/gallery2/phpinfo.php
Webserver (e.g. Apache 1.3.33): Apache
Database (e.g. MySql 5.0.32):mysqli 5.1.62-community-log, lock.system=flock
Activated toolkits (e.g. NetPbm, GD): ArchiveUpload, Exif, Getid3, ImageMagick, LinkItemToolkit, NetPBM, Thumbnail, Gd
Operating system (e.g. Linux):Linux host180.hostmonster.com 2.6.32-46.1.BHsmp #1 SMP Tue Sep 6 12:18:02 MDT 2011 x86_64
Browser (e.g. Firefox 2.0): Google Chrome 17.0.963.79 m

As I was trying to solve the problems in this thread: http://gallery.menalto.com/node/105816#comment-389183 I logged in (manually--still can't login with the login link) and after trying to change my theme (which didn't change) I came back to my gallery and the directory tree on the left just shows "Expand | Collapse" and clicking on either does nothing. What did I screw up and how do I fix it?
--
WebKat, Gallery2 holdover extraordinaire.