i have a iphone 3g with 3.1.3 currently installed. i wanted to downgrade it to 3.1.2 by selecting my own software, but i restored it via itunes first, so it updated it to 3.1.3. now that it is fully restored, its giving me the "insert a sim" page and i don't have a sim. on itunes, its saying "insert a sim, then plug back into itunes". is there ANY way to over come this issue??