Hello,
Could you please upload the sylink.log, log.liveupdate and log.lue?
Check this Article on How to collect Logs -
How to enable Sylink debugging for the Symantec Endpoint Protection 11.x and 12.1 client in the Windows Registry http://www.symantec.com/docs/TECH104758
More detailed information about why LiveUpdate is failing can be found in the following log file:
These are found under:
C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate\Log.LiveUpdate
C:\Documents and Settings\All Users\Application Data\Symantec\Symantec Endpoint Protection\12.1.671.4971.105\Data\Lue\Logs
On Windows Vista, Windows 7, and Windows Server 2008:
C:\Program Data\Symantec\Symantec Endpoint Protection\<silo_id>\Data\Lue\Logs
A Quick look on this Article would help you with Symantec Endpoint Protection: LiveUpdate Troubleshooting Flowchart
http://www.symantec.com/docs/TECH95790
Hope that helps!!