Hi KAT,
One important note: the version of SEP you are using dates from September 2009 - three years old! There are thousands of fixes and improvements that have gone int SEP since then. I recommend upgrading SEPMs and clients to the latest release of SEP 11 (SEP 1 RU7 MP2) or to SEP 12.1.
These articles may also help, if they match your symptoms:
Removing duplicate clients from the Symantec Endpoint Protection Manager using the CleanClients tool
Article:TECH97371 | Created: 2009-01-11 | Updated: 2012-03-30 | Article URL http://www.symantec.com/docs/TECH97371
How to obtain a listing of Clients machines imaged with Symantec Endpoint Protection (SEP) 11.0.5 and later with duplicate hardware ID's
Article:TECH157434 | Created: 2011-04-05 | Updated: 2012-05-24 |
Article URL http://www.symantec.com/docs/TECH157434
Hope this helps! Please do keep your thraed up to date with the latest progress and developments.