From the 2nd link below.
This error is often related to USB timing. Try changing USB ports, using a different dock connector to USB cable, and other available USB troubleshooting steps (troubleshooting USB connections. If you are using a dock, bypass it and connect directly to the white Apple USB dock connector cable. If the issue persists on a known-good computer, the device may need service.
If the issue is not resolved by USB isolation troubleshooting, and another computer is not available, try these steps to resolve the issue:
- Connect the device to iTunes, confirm that the device is in Recovery Mode. If it's not in Recovery Mode, put it into Recovery Mode.
- Restore and wait for the error.
- When prompted, click OK.
- Close and reopen iTunes while the device remains connected.
- The device should now be recognized in Recovery Mode again.
- Try to restore again.
If the steps above do not resolve the issue, try restoring using a known-good USB cable, computer, and network connection.
Update and restore alert messages on iPhone, iPad, and iPod touch
iOS: Resolving update and restore alert messages
iPad: Unable to update or restore
Using iPhone/iPad Recovery Mode
Yes I have tried different cords and differwent USB ports. Only one of the 3 works at all and it has a different colour mini board inside it than the others. When the iPad was working porperly I don't know that any of the 3 ports didn't work.. I have purchased a few cords over time off eBay but I'm now only using the original white apple cords I got with my iphone and ipad although I don't know which is which any more. I never use a dock although my wife does when she syncs her iPhone. When you say a different computer altogether, it obvously needs iTunes but does it need to know my iPad. Could a new Mac work?
When you say the device might need a service, what does that actually mean? I have thought that the iPad terminals might be dirty or something because it stopped being recognised by the PC as a hard drive and also iTunes. But after attempting a recovery it is now at least being recognised by iTunes in as much as prompting a message in iTunes that it needs restoring. If that makes sense.