Okay, now this is really driving me crazy. It works on your Event Calendar and DOM (http://dataobjectmanager.carlinowebdesign.com) sites, although I swear this morning when I tried it on that second test site it also didn't work there.
My site still isn't working, and I've updated from your SVN at least twice today. I've ran a DIFF of the files your SVN says you have changed and they all seem to appear in my files also. I'm pretty sure I haven't made any changes that would affect things loading in the admin side (only custom template files for the front end).
I've ?flush=all and went into /tmp/ to remove all the temp files SS uses in case of weird caching issues. I've also cleared out my browser caches, and it doesn't work in my system on either Safari or Firefox, but seems to work in both on your sites.
I'm gonna continue to dig into it, has to be some css/js thing. It appears all the requirements are loading, etc. It's driving me insane though, as it worked totally find in 2.3.1 with a snapshot of your modules from a couple months back.
I'm testing both in the vanilla Event Calendar, and in a module I created for our site. Same effect in both locations.
If anyone has any ideas, please share!