Was tinkering around at work just now and stumbled on a conflict. I couldn't get my work iTunes to update my iPod here at my work iMac, but my personal laptop could connect with my iPhone. I had NetBarrier set to No Restrictions and still wouldn't connect. What I found is if you have the "Banner Filter" enabled iTunes won't connect to the update server. So if yah can't update try turning that off that feature if you having iphone update issues, the rest of the firewall can remain on.