We are getting numerous reports regarding error 3002, error 3200 while updating to iOS 5. It turns out that these errors are due to overwhelming response of iOS 5 installation and activation worldwide. Apparently Apple servers are throwing errors randomly. Father of Jailbreak aka Saurik also confirmed the issue “ To anyone getting "An internal error occurred." (3200) while installing iOS 5.0, Apple’s servers are swamped, and failing half the requests. “
If you are also getting the same error, don’t panic and try again after some time.