I don't think it's the iPhone 4 causing the trouble, I think it's your computer or specifically iTunes.
Generally, when I have a problem with iTunes I either check for an update (make sure the iTunes on your computer is the most recent version). If that doesn't do it, you could always just reinstall iTunes. This will clear up most problems. Just uninstall iTunes, then go to apple.com and install a fresh copy of the software.
Hope everything works out for you.
08-17-2011 02:59 AM