To my knowledge the version of TinyMCE changed to 3.5.12 in Omeka 2.5 (think it was 3.5.11 in Omeka 2.41).
In Omeka 2.5 we have encountered an issue where the object selection dialog in blocks with objects in ExhibitBuilder won’t show on IE 11. The user clicks the ‘+’-icon but noting happens and IE throws an ‘undefined error’ for tiny_mce.js (see included screenshot).
I tried replacing ‘tiny_mce.js’ in ‘/application/views/scripts/javascripts/vendor/tiny_mce/’ with version 3.5.11 and this seem to solve the issues in IE11.
Is this something you are able to reproduce?
I can confirm the error… it’s something fairly specific because it only seems to happen on the Exhibit Builder’s page edit. It seems that it doesn’t like activating the editor for the Caption attachment option… possibly because it’s hidden?
TinyMCE is a problem area because they aren’t working on the 3.5 branch at all, so there’s basically no chance for a 3.5.13 that would fix the issue. I’m somewhat loath to downgrade it, but that may be the best short-term solution.
Understandable 
We’ll downgrade temporarily anyway and keep a close eye on any issues that may arise.
I was able to solve it by moving j.addRange(k) inside the try{j.removeAllRanges();}catch(h){} block. Not really clean or clever, but I couldn’t find any negative side-effects, yet.
