Update to iOS 5.0 fails repeatedly, why?

Question

The error message says "network connection timed out" when it hasn't. it always stops after 668.7 of the 668.8 download. I have tried on different network (although on the same lap top)

Answer 1

Disable Firewall and Anti-Virus
This is often the simplest solution and this is what you should try first. Temporarily disabling your antivirus software and firewalls often works to cease the network time outs. I can’t give specific instructions for this because there are so many different types of antivirus and firewalls out there, but it’s usually just a matter of finding the program in question and disabling it. Obviously, once the iOS update has been run successfully, you’ll want to re-enable the firewall or antivirus.
Uninstall and Re-install iTunes
This seems to be more effective for Windows users, but sometimes just uninstalling iTunes and re-installing the latest version is enough to resolve network connection errors.
Flush DNS Cache
Sometimes flushing your DNS cache is enough to resolve the network time outs, here is how to do this for Mac OS X and Windows:
Flushing DNS Cache in Mac OS X
We’ve covered this before but here’s a reminder:
Launch the Terminal from /Applications/Utilities
At the command prompt, type in “dscacheutil -flushcache” and hit return
After the command has executed, you can exit Terminal and your DNS has been flushed
This works in Mac OS X 10.5 and Mac OS X 10.6 or later.Flushing DNS Cache in Windows XP, Vista, and 7
Go to the Start menu and click on “Run”
In the “Run” box, type in ‘command.com’
When the DOS prompt appears, type in ‘ipconfig /flushdns’ and hit return
If the command has run properly, you’ll see a message saying DNS Resolving Cache has been flushed
You can now close the command.com prompt window
Note: if you encounter an error in Windows saying you do not have permissions or need authentication, make sure you run command.com as an Administrative user. You can do this by right-clicking on Run and selecting “Run as Administrator.”
Manually Download the iOS Update
If you’re having problems downloading the update file (IPSW), you can actually download these directly from Apple rather than through iTunes. This is recommended more for advanced users since there are so many versions of iOS and firmware available, but here are the repository links:
iPhone Firmware IPSW file downloads
iPad Firmware & IPSW file downloads
iPod Touch Firmware & IPSW file downloads
If you go this route, here is where the IPSW files are stored locally on your machine:
IPSW location in Mac OS X: ~/Library/iTunes/iPhone Software Updates
IPSW location in Windows XP: \Documents and Settings\username\Application Data\Apple Computer\iTunes\iPhone Software Updates
IPSW location in Windows Vista & Windows 7: \Users\username\AppData\Roaming\Apple Computer\iTunes\iPhone Software Updates
This is where a corrupt or half-downloaded IPSW file will sit too, but you should backup the existing IPSW file before overwriting it with a new version just in case.