I just recently bought an iphone4. It came installed with 4.2.1 firmware, and since 4.3.4 is released now it is not as simple as to just update the firmware with itunes. I have tried some good which tells you to use tinyumbrella, but I didn't got it to work. As I got error message 1604 when trying to restore. Anyone know how to upgrade to 4.3.3 firmware?