This method will help you solve the common, Internal Error and Unknown Error that pops up on iTunes when you try to upgrade to iOS 5 on your device.
iOS 5 was unveiled to the public with over 200 new user features and a lot of API and UI improvements. Being a major release, many are trying to install the OS onto their iDevice and have been facing this error.
Some of the most common errors that iTunes is popping-out now are the Internal Error and Unknown Error 3004 and many others alongside these errors. These errors are not really from your side or not because of the host file on your Mac or PC.
These two particular errors are server side errors and are not in our control. The error occurs when a lot of users try to restore their devices and the server fails to handle the load in signing your device’s UDID. The only solution known right now is to wait for the servers to free-up and try restoring again after sometime.
Apple‘s servers get too busy when they release a new version of iOS to their users, as millions and millions of iDevice owners try to restore their device all at the same time.
So all you can do right now is to wait for sometime and try restoring again!
You can also find solutions for some other iTunes errors here. [/alert_box]
You can also follow Karthik on Google+ of Facebook or Twitter.