Okay, so last night I updated to 10.6.3. A couple hours later, I closed down iTunes and opened it back up to discover that it wouldn't open anymore. I tried removing the library file, thinking it might have become corrupted somehow, and iTunes would sort of half-open, but not for long. And then when I'd try to open it up again, it would crash. At this stage, I could get it to briefly open every time by removing all the library files every time, but then it would recreate them, and when it close/crash (and it would do this every time fairly quickly), it would once again not open at all unless I removed the library files. At this point, I tried this: http://support.apple.com/kb/ht1224 to entirely remove all traces of iTunes, and then reinstalled the latest version, 9.0.3. Now, the problem was actually worse; it would ONLY open to the point where it would ask me to agree to the iTunes EULA, and then after I did, it would immediately shut down again. At no time in this process, by the way, did it EVER give me an "iTunes shut down unexpectedly" message. It NEVER gave me the option to "ignore, report, reopen." So I'm not even entirely sure if it crashed; iTunes might've simply found something it did not like and decided to close. I am not sure. Next, I tried reinstalling the 10.6.3 update all over again, uninstalling iTunes from scratch all over again, AND restoring my System files from an older save on Time Machine. Still nothing. I've restarted innumerable times, uninstalled and reinstalled from scratch several times. I suspect (though cannot know for sure) that what caused iTunes to refuse to stay open anymore was related to my having used Monolingual. I've used Monolingual many times over the years and not suffered for it, but it's the only thing that makes sense, because iTunes opened fine originally when I'd first done my restarts after updating, but then when I simply shut down and reopened the application once it wouldn't work anymore. Since Monolingual works while other applications are open, I find it most likely that it removed something necessary that iTunes needed. Just for the record, what I used it to remove this particular time were as follows: all languages except French, English, and Swedish, and all architectures except ARM and Intel. I suspect this latter move was what did it, but I have no idea why, as I've done it once before and it was fine. The only other thing I can think of that could possibly be related is my having installed Final Cut Express last night, but I seriously doubt it. Can anyone help? I feel as though I've tried everything!