Hello, I have an IPhone 3G, 2.2, baseband 2.28. I used Quickpwn to jail break and then used yellowsn0w to unlock through cydia. It worked fine for a few days, then for some reason it began to display and error saying "invalid sim" when any sim card is in it even an ATT sim card. A litte while after that it just simply wont boot up, it displays the apple logo statically and doesn't boot up. Please let me know if there is anything i could do. Also, I tried a hard reset to no avail it just turns off. I also tried connecting it to itunes and it doesnt seem to be detected by itunes. This is a nightmare, please help if u can!