HT4623 Why do i keep getting this error message when trying to update to ios 5.1 "unable to install update"?

Question

Ive gotten this when trying to update while connected to iTunes and when I tried to update through general.

Answer 1

Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
Select
/var/log ▹ appstore.log
from the hierarchical list on the left. If you don't see that list, select
View ▹ Show Log List
from the menu bar. Then select the messages from the last installation or update attempt, starting from the time when you initiated it. If you're not sure when that was, click the Clear Display button in the toolbar of the Console window and then try the installation again.
Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message (command-V).
If there are runs of repeated messages, post only one example of each. Don’t post many repetitions of the same message.
When posting a log extract, be selective. Don't post more than is requested.
Please do not indiscriminately dump thousands of lines from the log into this discussion.
Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.