Mine is a 8GB 2G MC model. After using umbrella and modifying the host file to set up local server to host shsh blobs (because i have my shsh file in computer, not on saurik's server), i put it in DFU mode (and im sure it is because the screen is black) and tried Shift + Restore and point to the 3.1.2 firmware. after a while, the screen turned white and after a while, the apple appeared with a bar below it showing the restoring process. that's when i got the error 28. i tried many times but still have same error. pls dont tell me that it's a hardware problem 'cause i tried to use the default itunes restore and it got restored to ios 4.0 smoothly.