I know this topic has come up a lot, but I feel like my case of it might be slightly different and wondering if anyone else has found a fix to my scenario. I cannot update my phone, (or another phone that I tried), to any ios, not even the same one. I'm trying to restore to a custom ipsw, not that it's super important. I've tried updating to the newest version of iTunes, though I'm just trying to restore to ios 5.1.1 anyway, so I don't think it's required. I've tried editing the host file a billion times as described. adding # before the apple lines at the end, or just deleting the apple lines and saving and replacing the file. I have done jailbreak related stuff on my desktop mac and my macbook, but I get the same error when trying to update on a friend's macbook pro who has never had any kind of jailbreak related programs opened. I've used tinyumbrella in the past but the option about getting files from Cydia is unchecked. The phone I'm currently trying to make useful has never been jailbroken and I can't update it still. I've been researching this for hours and hours, and still can't get anything to work. Any help would be greatly appreciated!!