Hello,
Are these clients able to communicate with Symantec Endpoint Protection Manager properly?
What version of SEP 11.x are you running?
Are these clients receiving updates from SEPM / LUA / GUP?
Check these Articles:
Symantec Endpoint Protection: LiveUpdate Troubleshooting Flowchart
http://www.symantec.com/docs/TECH95790
How to create a client installation settings to delete previous logs, policies and reset the client-server communication settings?
http://www.symantec.com/docs/TECH93617
Incase, if you want to clear all the definitions and reinstall the Latest Definitions, then try
Using the "Rx4DefsSEP" utility (Tool available with Symantec Technical Support)
http://www.symantec.com/business/support/index?page=content&id=TECH93036&locale=en_US
In that case, I would request you to Call Symantec Technical Support. Once you have the Case #, simply PM the Case number and I assure you would receive the "Rx4DefsSEP" Utility.
How to create a new case in MySupport
http://www.symantec.com/business/support/index?page=content&id=TECH58873
Phone numbers to contact Tech Support:-
Regional Support Telephone Numbers:
United States: https://support.broadcom.com (407-357-7600 from outside the United States)
Australia: 1300 365510 (+61 2 8220 7111 from outside Australia)
United Kingdom: +44 (0) 870 606 6000
Additional contact numbers: http://www.symantec.com/business/support/contact_techsupp_static.jsp
Hope that helps!!