I installed iOS5 to see what it was like - it's OK, but I'm not overly impressed with it on my 3GS. Prior to this upgrade, I was running 4.3.3 Jailbroken. I have all of my SHSHs saved locally as well as on Cydia. I'm using Tinyumbrella to try and downgrade. iTunes unpacks and verifies the 4.3.3 firmware (which is the official IPSW file), then reboots the phone. As soon as this happens, the DFU screen appears on the phone, and iTunes gives me an error 20. Am I missing something here?