Im on a iphone 3gs firmware 3.1.2 and whenever i jailbreak it with blackra1n everything works until it just shuts off. It doesnt bring me to a lockscreen like its suppose to. It worked before but when i installed winterboard and it had to restart it doesnt work anymore. I tried to restore the firmware 3.1.2 in itunes but it wont let me. it says "this device is not eligible required to rebuild" or something along those lines. What can i do to get the iphone back to normal state without restoring to 3.1.3?