Now you can jailbreak iPhone3GS with old bootrom on the latest iOS 4 firmware. The creators of the original PwnageTool has confirmed that this version has been modified and redistributed without their permission,
and i recommend that iPhone 3GS users who are jailbroken using Spirit, and with new bootrom should avoid upgrading to iOS 4 until new jailbreak tools are available.
What would be considered “old boot rom” i have a 3gs with modem firmware 5.11.07 or 3.1.2 (7D11)
The MCXXX