You'd have to speak with the people who do the script/theme. Version updates often break a few things and its up to the scripter to rewrite the code to make it work.
My guess would be the change in API, since the loading and precompiling seems to use a dll. I haven't tried to switch lately, since my current theme works.
As far as I know dlls should still work. Khaled said that dlls must explicitly state they want unicode support and if said support isn't requested, then it defaults to the old behaviour.