Source Code broken on TinyMCE Advanced in WP 4.0

Works properly here… Maybe empty the browser cache, then if still no-go:
– What browser?
– Any errors in the browser console?

For the past year I have used the Source Code function to collect HTML for our long articles and make a local backup. Since updating WordPress to 4.0 this function now displays an empty dialog box, instead of HTML code. It happens in the current versions of Chrome, Firefox, and IE. No errors are reported. I’ve tested this on three different computers, and the function still displays an empty box instead of HTML for the post.

I have emptied all site caches, cleared browser caches, and even restarted my server. It worked perfectly prior to the update, and now it doesn’t.

UPDATE: After I checked some of my other WP sites and noticing that this function works on them, it appeared that the issue was local to my site/installation. I hadn’t installed any new plugins (aside from post 4.0 updates), so I began disabling plugins until I found the problem.

As it turns out, the plugin “NextGEN Gallery by Photocrati” (Version 2.0.66.27) was to blame. I’ll message them about the problem as well, but there might be something in your code that should be separated from their code calls.