Unable to update iPhone 4, iOS 4.2.1, iTunes 10.1 (54), Mac oS 10.6.5

splurben solved his own issue.  Great work!

I fired up my G5 MacPro and was able to update the phone, I was also then able to determine the download location for iTunesiPhone updates which is

~/Library/iTunes

When I saw that I also noted that the permissions on that directory was Read/Write for System only, I added Read/Write permissions for Staff and then the download was able to happen.

Apple needs to amend the Repair Permissions programme in Disk Utility to ensure that the above directory ( ~/Library/iTunes ) is Read/Write for Staff or users won’t be able to carry out iPhone updates.

I haven’t had a chance to try the new printing features, however, my Bluetooth headset performance is dramatically improved with the iOS 4.2.1 update.

via Apple – Support – Discussions – Unable to update iPhone 4, iOS 4.2.1, ….