iTunes error code 2

Hi guys.

I hope someone can help me I have an iPhone 4 I recently purchased as spares or repair.

It is stuck in DFU mode but when I try to restore it I get this

the iphone iphone could not be restored. an unknown error occurred (2).

I have tried all sorts to get round it it's supposed to be an issue with antivirus but I don't have any antivirus as I only use Mac.

I've tried on both my iMac & my MacBook Air neither of which have antivirus or any firewall set up.

Interestingly on the iMac I get a different error code I get error 21.

Problem with the iMac is I use it as a server in my workshop so it has a lot of drives & devices plugged into the FireWire & USB ports to unhook it all would be a pain.

But the MacBook Air has nothing plugged into USB except of course for the iPhone.

Other things I have tried iReb I have also removed the logic board from the iPhone & hooked a battery with a dock port to it & tried the restore that way no joy same error code.

Anyone maned a workaround or found a way past this?

Thanks guys