I remember iphone can get 速成 in and use,but forget how...
JB already, but 3.1.3..... you are 3G or 3Gs?
3Gs.... you have to wait
when you still is 3.1.2 or something like that, restore just have to download the firmware which you want,
than in itunes press Shift + restore, choose that file is alright, but if you just press that upgrade to 3.1.3......