I had similar problems for the last couple of patches and I tried to reinstall different options to see what was causing this, but it turned out that the permissions on the battle_elements,xml in the gui folder of the res_mods folder got messed up.
You can find these if you right click the file, go to Properties, select the tab Security and edit that.
There should only be permissions for Everyone, with everything checked to allow to make it work. In my case there were two other entries which were just weird and I'm guessing the installer messed that up when creating the file.