We read all over the net and found some solutions to the most common issues that occurred. If you are kinda conservative user, we’d recommend not to update to firmware 2.1 and wait until a PwnageTool and QuickPwn update has been released. Since the iPhone Dev Team is reacting very fast, this should take only some days.
Error 1600 and Error 6: restore with stock firmware 2.1, then QuickPwn (you may then put into restore mode and install custom IPSW, but it’s not necessary- credits to “HomeGrown”).
Error 1600: when Pwnage asks, if already pwned your device, answer NO, no matter if you pwned if before or not (credits to “Maurofoto”)
Error 1600: let iTunes download firmware 2.1 again (you may delete it from the local folder if you already downloaded it via iTunes. Folder on a Mac:
~/Library/iTunes/iPhone Software Update/), then exit iTunes, prep a custom IPSW using Pwnage, delete the iTunes downloaded firmware from the above mentioned folder again and copy your custom IPSW to that folder, but name it exactly as the original firmware was named (credits to “Markat”)