Update: The problem seems to occur when you try to restore to an iPwned ipsw from a non-iPwned device. Syncing to an already Pwned device works fine.
Editor's note: The sentence above which states that the Dev Team's efforts are becoming "less relevant" is not an opinion which is endorsed by Engadget. Quite the contrary -- many of the editors here are die-hard fans of PwnageTool and the Team's work, and believe that their contributions to the iPhone community are hugely important. Thomas -- who lives in The Netherlands -- has a point in regards to users who previously had no access to the phone and were forced to import and unlock, or more casual users who likely find the App Store more approachable. Personally? I don't update my phone until the Dev Team has worked their magic, and they have Engadget's full support and respect. -- ed.