Hi,
As per attached logs two errors are commonly seen
[Date] [Time] -> EVENT - SESSION END SUCCESSFUL EVENT - The LiveUpdate session ran in Express Mode. LiveUpdate found 0 updates available, of which 0 were installed and 0 failed to install. The LiveUpdate session exited with a return code of 100, LiveUpdate ran successfully. There are no new updates to your products.
[Date] [Time] -> EVENT - SESSION END SUCCESSFUL EVENT - The LiveUpdate session ran in Silent Mode. LiveUpdate found 2 updates available, of which 2 were installed and 0 failed to install. The LiveUpdate session exited with a return code of 1800, Success
Follow this article :
http://www.symantec.com/business/support/index?page=content&id=TECH158623