Managed to fix the issue, but it was not pleasant. In the event anyone runs into this, the problem was that I had installed a template that was compatible with PS 1.5.x, but then upgraded to 1.6.x. Long story short, those Javascript modules broke big time between the transition.
Ended up having to roll back to 1.5 and redo a lot of the work. In the future, I guess it pays to be wary of updates.
My question is, is there any way to prevent modules from forcing you to update when you're on an older build of Presta? There has to be some way to upgrade things without having to reinvent the wheel with new themes every single time you upgrade Presta?