ipad 2 stuck in DFU mode with error 9

My iPad 2 decided to stop working in that when I switched it on, it would only go as far as to show the apple logo and no further. I followed the instructions here to put it into DFU mode and do a restore or update from iTunes. Everything looked good until it got to the part in the process where it validated the installation with the Apple servers. At this point iTunes would pop-up an error box showing "The IPad could not be updated. An unknown error has occurred (9)". I've followed the instructions on the KB for troubleshooting (checked my USB, tried different cables, tried a windows PC and a macbook pro, switched off all AV software etc), but nothing works. I've attempted this several times now and it won't budge so does anyone else have any advice for me? The nearest Apple centre is over 1.5hrs away and they don't have any appointments for about a week.