According to this article:
iTunes: Specific update-and-restore error messages and advanced troubleshooting
These errors are typically resolved by performing one or more of the steps listed below:
- Perform USB isolation troubleshooting, including trying a different USB port directly on the computer. See the advanced steps below for USB troubleshooting.
- Put a USB 2.0 hub between the device and the computer.
- Try a different Dock Connector or Lightning Connector to USB cable.
- Eliminate third-party security software conflicts.
- There may be third-party software installed that modifies your default packet size in Windows by inserting one or more TcpWindowSize entries into your registry. An incorrectly set default packet size can cause this error. Contact the software manufacturer that installed the packet-size modification for assistance. Or, follow this article by Microsoft to reset the packet size back to the default for Windows:How to reset Internet Protocol (TCP/IP).
- Connect your computer directly to your Internet source, bypassing any routers, hubs, or switches. You may need to restart your computer and modem to get online.
- Try to restore from another known-good computer and network.
The iPad is connected directly to my Quad Core iMac, I have tried all of the ports and there is no difference to the issue.
Attempting to use a hub results in the same problem.
Different Doc Connector cable results in the same problem.
Restarted iMac will no third party programs running, no change in problem.
Connect to internet directly, no hub, same fault.
Try to restore from my MacBook Pro, same fault.
Any other ideas? Thank you for the thoughts!