Problems updating to iphone 4.1 on 3G iphone

Right now I have iphone 3G. I would like to upgrade its software with the latest iOS (4.1). For this I followed a website instructions and connected my computer with this iPhone and had a message saying 4.1 update is available for me. But the problem is that whenever I try to click on "Update", I have a window appearing with the message 'Backing up iphone'. However this process never ends up and I think this hangs. I also noticed that the green progress bar stops then and there itself. What happened to my iPhone? Since I have changed or installed nothing on it, then why is it happening to me?

Go to ~/Library/iTunes/iPhone Software Updates and remove all the .ipsw files that you can see. Ideally you must be having only one such files but still see if you have more than one and trash it. If you can't see the files then turn on show all hidden files & folders to view them. Just try to update it once again. Thus you are forcing iTunes to download the .ipsw file once again.

This certainly seems to be iPhone 4.1 bug, I think you need to take your iPhone to the Apple support team to look into the matter. I hope they have come across with this problem and have some solution to fix this problem. Once I had some problem with my iPhone and had an error 29. When I discussed about the problem with Apple technical support team and they suggested me that its due to faulty cable.

Although you have not installed or downloaded anything on your iPhone, but still you are using your computer which has a iphone 4.1 downloaded that may be faulty which is creating the problem. If you have not downloaded the software from Apple then I would suggest to download it from there. If you have downloaded it from Apple then I would also like to tell you that you should try out the instructions mentioned on the Apple site itself rather than checking any other website for the same.

Here is how you upgrade to iPhone 4.1 :

1. Make sure you are using the latest version of iTunes. Connect your iPhone to your computer.

2. When iTunes opens, select your iPhone under Devices in the Source List on the left.

3. In the iPhone Summary pane, click Check for Update.

4. Click Download and Install. Do not disconnect your iPhone until the update has finished.