Every time I've loaded iTunes 10.5, and now still iTunes 10.5.1, I get this error message: A required iTunes component is not installed. Please reinstall iTunes (-42403) I also get this error when I try to load the iTunes store: iTunes could not complete this Store Request: and it gives some error code (can't get it to reappear, happens randomly) I've tried reinstalling, messing around and deleting key plist files and preference documents, and I've even gone so far as to try to have the Apple Store geniuses (who, I must admit, aren't that genius---all they did was format the drive, back up in Time Machine, and put everything back...like that would help me at all), and fully erasing iTunes from my computer. I keep trying to reinstall, and nothing happens. If maybe iTunes would lend some help into WHICH component is missing... Any help, please? I can't sync my iPods and iPad, and there is data in my iTunes library to large for iCloud to handle. Please, constructive comments and replies only. Thanks!