Iphone 3g showing error -1. Help. Wont restore

I have connected to itunes which recognises the phone, gives me the option to restore. It then goes through the process and at the very end it says "It could not be restored. Unknown error occurred (-1). The phone is now stuck on a screen showing a usb cable and the itunes logo. I cannot go anywhere from here. I have got it into DFU mode and the same thing happens.

since downloading ios 6 the phone has been continually resetting itself and restoring to factory settings. It doesnt even do that anymore

Anyone got any suggestions?

thanks