Unknown error -1 when restoring in recovery mode?!

Hello,

After a screen replacement on an iPhone 4S, the phone failed to say INSERT SIM when the sim card was removed. Instead it constantly said SEARCHING, and never found the carrier (EE). I checked all hardware and noticed nothing unusual. All antennas etc were connected fine. Wifi worked too.

I googled the problem and was told to do an update to iOS6.1 from iOS6.0 - this failed when doing it via the phone, so their suggestion was update it via iTunes.

I plugged the phone into iTunes and did the update, however it failed and left the iPhone with no OS, and only the logo to plug it into iTunes.

So, I plugged the iPhone into iTunes, which said it's in recovery mode, and that I must click the only option - which was to restore the iPhone.

I clicked this.. waited for a long duration.. to be left with an "Unknown error (-1)" as it failed. I tried to do this restore in recovery mode several times on several different computers running different Windows OS's.

Unfortunately I've had no joy with this! How can the restore fail in recovery mode?! And what is unknown error -1 ??

Thanks in advance guys,

Josh