G2 exploded on me... help?

This gallery is used in a Joomla! site, and just suddenly up and stopped working one day. It's frankly been a long time since I installed and I have no clue what is wrong or how to fix it...

Upon logging in with admin account, browser displays:

Error

An error has occurred.

Back to the Gallery
Error Detail -
Error (ERROR_COLLISION)

* in modules/core/classes/GallerySession.class at line 702 (gallerycoreapi::error)
* in modules/core/classes/GallerySession.class at line 305 (gallerysession::_acquirenewpersistentsession)
* in modules/core/classes/GallerySession.class at line 488 (gallerysession::start)
* in modules/core/classes/helpers/GalleryUserHelper_medium.class at line 327 (gallerysession::regenerate)
* in modules/core/classes/helpers/GalleryEventHelper_simple.class at line 117 (galleryuserhelper_medium::handleevent)
* in modules/core/classes/GalleryCoreApi.class at line 2132 (galleryeventhelper_simple::postevent)
* in modules/core/UserLogin.inc at line 143 (gallerycoreapi::postevent)
* in main.php at line 231 (userlogincontroller::handlerequest)
* in main.php at line 94
* in main.php at line 83

System Information
Gallery version 2.2.1
PHP version 4.4.7 cgi-fcgi
Webserver Apache/1.3.39 (Unix)
Database mysqlt 4.1.21-log
Toolkits ImageMagick, NetPBM
Operating system FreeBSD pro33.abac.com 6.2-STABLE FreeBSD 6.2-STABLE #1: Wed May 16 17:21:55 PDT 2007

:/var/obj/usr/src/sys/PRO6 i386
Browser Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.7) Gecko/2009021910 Firefox/3.0.7