There must be a conflict somewhere with the variable name used in the "imagegallery_init.js" with something else being used elsewhere. I just changed gallery to mygallery and everything snapped into place.
Oddly, it was just IE throwing the error here as firebug showed no problems.
Yeah, I was just looking at that. It's kind of weird that function doesn't use jQuery. I can see what I was thinking, making it framework-independent, but since so many of the plugins are jQuery based anyway, maybe I should just require it. That way, naming collisions like that won't happen.