try to hard reset the device and then try the update again, also try to uninstall Zune and then re download and install it before reconnecting the arrive. try the second thing first then try the first if no luck. u can also look in the Microsoft knowledge base, they usually have a collection of error codes, what they mean and how to solve them.
EDIT.
found an article that describes how to solve the problem,if this doesn't work then do what I said above.
http://support.microsoft.com/kb/2484...811A5_801881CC