Hello,
What version of SEPM / SEP 11 are you running?
I believe you are talking about this Issue -
The Symantec Endpoint Protection (SEP) client is unable to update if its Group Update Provider(s) (GUP(S)) have temporarily been unreachable.
http://www.symantec.com/docs/TECH182527
Make sure you are running the Latest version of SEP on all machines i.e; SEP 11 RU7 MP2
I would request you to check this Article:
What happens when both LiveUpdate Server and Default Management server are configured in a LiveUpdate policy?
http://www.symantec.com/docs/TECH140817
How to update virus definitions and other content with Symantec Endpoint Protection and Symantec Network Access Control
http://www.symantec.com/docs/TECH102467
Symantec Endpoint Protection Manager - LiveUpdate - Policies explained
http://www.symantec.com/docs/TECH104435
Hope that helps!!