Make sure that in Connections Tab of Internet Options there is no Proxy configured if you are not using any.
Other than that check the following
In C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate, open and edit "Settings.LiveUpdate"
Go to the end of the file and edit the following parameters:
PREFERENCES\INTERNET_CONNECT_TIMEOUT=45
PREFERENCES\INTERNET_READ_DATA_TIMEOUT=45
Set them to:
PREFERENCES\INTERNET_CONNECT_TIMEOUT=200
PREFERENCES\INTERNET_READ_DATA_TIMEOUT=200
Save and close the file.
Then run LiveUpdate