Many users have reported an unknown error message (1602) when attempting to update their iPhones to firmware versions 1.1.3 or 1.1.4. Though there are many documented approaches to solving this problem, none seems to work for everyone. Our readers have reported success using the following approaches:
1) Reset sync history (instructions here)
2) Turn off Auto-lock on the iPhone prior to attempting an update. There is no indication why auto-lock being on would affect the update process, however.