Edit: Didn't notice Mr. Lizard had already posted this: Stratus, do you know if the system will boot if we replace everything but HIToolbox? (Not to say that the other files wouldn't crash iTunes given the chance, but we do have a primary suspect here.)
I don't think it will. A few months ago when I was originally trying to figure out how to get the menus back after reading this thread, I first tried replacing CoreUI only and things wouldn't boot up. If I did it in place while already logged in, programs would crash and cite HIToolbox as the reason. The two are completely linked, it seems.