Resolve communication issues
Check the hosts file or TCP/IP filtering, which might cause communication issues between iTunes, ports, and servers.
Common errors: 1004, 1013, 1638, 3014, 3194, or 3000-3999. These alerts refer to gs.apple.com, say "There was a problem downloading the software", or say the "device isn't eligible for the requested build".
See first link below.
iTunes: Specific update-and-restore error messages and advanced troubleshooting
http://support.apple.com/kb/TS3694
If you can’t update or restore your iOS device
http://support.apple.com/kb/ht1808
Cheers, Tom