I have an IPSW file of 6.1.2 downloaded and I'm running 6.1.3 on my iPhone 4 and I put it in the dfu or something mode and then press shift and choose it but then an error pops up after verifying the software. I have no clue what is wrong with it and I really want to jailbreak but can't till this first step is complete. HELP!?!?!