The Error 3002 is one of the common problems that users of iPad, iPod or Iphone will get during their attempts to upgrade their device to the new iOS. When the problem appears, it flashes a small window that says your device cannot be updated due to an unknown error. When this happens you won’t be able to compete the upgrade without finding a great solution first to fix the issue.
There is no concrete basis yet on what exactly is causing the problem and this is why when it happens to your device it is best that you just find ways to fix it. In order to resolve the issue you must first restore your device instead of doing the upgrade. And always remember to make a backup of all your data before changing anything in order to prevent losing files.
What you can do to restore your device is first to make sure that you have already installed iTunes 10.5 on your Mac. Once it has already been completely installed you may then launch iTunes and take a look at the left-hand column of the window. Once you see your device just click on it and the “Restore” button. You will actually get a warning from Apple that your action will reset the unit to its factory settings and all you have to do is to simply continue to restore. Once you confirm your action, iTunes will then take care of doing the rest of the job.
There shouldn’t be any problem at all during and after the process just as long as the servers of Apple are not flooded with requests. Once you have successfully completed the process and you want to regain your old data you can use your backup to restore your data. In order to do this, go to the left-hand column of the iTunes window and select your device by simply right-clicking on it. You may then click on the option that says “Restore from backup” and then choose the recent backup that you want to restore. It may take a while to have your content and apps reinstalled but once the process is done you can then use your device without any trouble at all.