I noticed that on WP 4.0 combined with NextGEN Gallery 188.8.131.52 the newsletter plugin triggers two js errors on the newsletter template editor.
I disabled all other plugins, so it has to be a conflict with NextGEN Gallery.
TypeError: tinyMCE.activeEditor is null
ReferenceError: jQuery is not defined
Because of the errors the auto updating of the new images in the preview breaks. Any ideas on how to prevent the js errors?