Last night I was updating my iPhone 4 to iOS 4.3 (from 4.2.1) and it got almost all the way through until it sought to verify the update with Apple and failed with error code 1013. The support document said this was likely to do with security software preventing iTunes from connecting to Apple but I had no problems with the iTunes Store (usually a dead giveaway) so I looked further and found that it’s to do with the hosts file on the computer needing a line edited.
I was just about to give it a try when I stumbled across references to the application TinyUmbrella causing this problem. I have used TinyUmbrella to grab the SHSH blobs for my AppleTV 2 so that I could jailbreak it safely (jailbreaking the ATV2 is highly advisable as it makes the device incredibly useful for things like XBMC). There’s actually a preference setting in the TinyUmbrella app that automatically alters the hosts file so that it forces checks to go through Cydia and not Apple and therefore allow jailbroken iOS software to go undetected.
Open the app, click the Advanced tab, uncheck the box marked ‘Set Hosts to Cydia on Exit’ and the update problem goes away.
Thought I’d post this in case it helps somebody else with the same problem without having to go editing the hosts file themselves.
