I’m getting this issue also. I just can’t get the overlay to load.
I have SP 2010 on prem. I’ve tried with ie11, firefox and chrome but always the same.
I load the NewForm to add an item, I get the Loading… Message then the This took forever! I click to close the message and the form doesn’t have any fields for me see, like it’s hidden everything and I can’t edit the form.
I’ve tried to look at the configuration list but there’s nothing in there.
In developer mode I get the error messages that have been reported earlier.
I’ve tried using the overlay code from Dec 2014 and also the code posted above but it’s still the same.
I’m expecting this to be a permission issue somewhere but I am the administrator of the site so I’m not sure how.
Is there any information or anything you want me to post to help find the issue? I’ve spent quite a bit of time on this but I just can’t seem to get it working.