You should use fu4m 1.3 fix-2 or at least fu4m 1.3 fix. But even the latest version of fu4wm doesn't work with the latest IBX (How to determine IBX version (WMP 10/11)).

So if fu4m 1.3 fix-2 doesn't work for you, you can try drmdbg with freeme2 or drm2wmv.