My friend, Mercedes, owns an iPhone 4 8GB (GSM) on AT&T. She received a notification last night from her iPhone 4, that there was an iOS update, and she told the iPhone to install it OTA. Her iPhone downloaded it, and went through the install process. Instead of booting back into a functional iOS, it went to the "Connect to iTunes" screen. Upon connecting it into iTunes on her Windows PC, she discovered her iPhone had booted into recovery mode. I spent 6 hours last night trying things. I manually downloaded the 5.1 and the 5.1.1 IPSW from Apple directly, only to receive an Unknown Error, with error code (1) from iTunes. I've also tried using RecBoot to kick the iPhone out of Recovery Mode, only for the iPhone to go right back into it. I've also tried restoring to 5.1.1, and 5.1 in DFU mode, though I get a new error, error 21. Apple is saying error 21 is related to security software. I've followed their instructions which say to disable it, for it not to work. She just came back from our local AT&T store, and they refuse to do anything. They're saying that her iPhone didn't download the update fully, and for her to download the IPSW from Apple, and restore it in iTunes. I tried that at least 10 times last night. Should I just have her go to the Apple Store? I wanted to make that a last resort, as the closest Apple store is 100 miles away. Also, I checked the iPhone Updater Logs in iTunes, and I didn't see any errors. What are some other steps I should try before going to a Genius? Also, should I try working on it with my Mac, instead of her PC? Thanks!