I ran into the issues with my iPhone 4S while trying to upgrade it it iOS 7.0.4 OTA and I have tried everything I can to recover it but no luck. I have tried different USB ports, different PCs altogether with av tuned off, and finally a MAC Pro this morning. I am stuck and miserable. I did everything that a number of forums have mentioned in terms of switching off anti-virus, clearing off host files, checking windows and mac firewall settings, setting the phone to DFU mode and trying over - you name it.
The error I run into most half way through the upgrade is "Unknown Error (29)". According to Apple (http://support.apple.com/kb/TS3694), it has to do with anti-virus but last night I spent 2 hours building an image with no av or firewall running and tried and still ran into the error. Even tried "Fix it" from Microsoft to clear off the host file configurations as prescribed.
Any help is welcome. Much needed.
So I got myself an appointment at an Apple store. The key this time was that the Apple Genius associate did a "forceful" install using a MAC Air which he claimed was engineered to do a straight install vs trying to restore a bricked phone. It's like installing OS on a new phone that comes off assembly line. That did it! The phone was up and running and I was able to sync everything (except account details) onto the device using iCloud backup.
So if you are having issues mentioned in thread, get an appointment and ask them to do a forceful or new install instead of reviving a bricked device.