Post/Page Visual Editor Not Displaying

I know this doesn't apply to WPMUDev, but I'm working with someone TRYING to help them figure out why something is not working on this website:

I've seen this before and all the things I've done in the past as well as everything I've tried from hours of research has failed to fix the problem. When editing a post/page, if you are in the visual editor, the content is blank and the buttons for the visual editor do not show. If you then switch to the text editor, it's blank as well. Usually when this happens, you can "highlight" the text and it will show up (because it's actually white not black). But, the only way to see this is to do a screen refresh after switching over to the text editor.

If you then switch back to the visual editor, you still see nothing. Refreshing the screen doesn't show anything either.

This is what I know for certain - it is specific to this theme - I can switch to Twenty Twelve and it works just fine.

I have done a lot of poking around and to the best of my ability to figure out, it seems that jQuery/javascript is not loading properly. I suspect that the theme developer is calling jQuery in the wrong way, but I have poured over the them code and can't seem to figure it out.

Does anyone have any insight on this? Is there a quick way for me to figure out where/how they are calling jQuery (assuming they are).

BTW, the theme developer is absolutely worthless. Why? Their reason is that the theme has been modified from what it was originally. Well, of course it has been. That's what we do to configure any theme for our clients. I've never had a theme developer refuse to help simply because I had modified the theme in some way.

Any help would be greatly appreciated.