If you open your client and go to Help >> Troubleshooting >> Versions
You will see the Definitions window. You can comapre what's here with the links from below to ensure you have the latest defs.
The home tab in the SEPM will also show if you are up to date or not
Latest AV definitions:
http://www.symantec.com/security_response/definitions/certified/
Latest IPS definitions:
http://www.symantec.com/security_response/securityupdates/list.jsp?fid=sep
The latest is RU7 MP2 for 11.x and Latest for 12.1 is RU1 MP1
Release Notes and System Requirements for all versions of Symantec Endpoint Protection and Symantec Network Access Control
http://www.symantec.com/business/support/index?page=content&id=TECH163829