Everything was working just fine, then, really not sure what happened (no changes to the code or theme). Now, none of the Lightbox images work. They start to open, then the page hangs with a white box.

Running through Chrome's Developer Tools, I get:

Code:
zen_lightbox_mootools_custom.js:235Uncaught TypeError:  undefined is not a function
In Firebug I get:

Code:
can't convert undefined to object
Running 1.3.9g (no time to update to the latest codebase)

Any thoughts on what's wrong?