See this KB, it may clear things up for you.
Still Infected status not clearing on Symantec Endpoint Protection Manager home page -
http://www.symantec.com/business/support/index?page=content&id=TECH95463&actp=search&viewlocale=en_US&searchid=1292606986700
About the Symantec Endpoint Protection Home page -
http://www.symantec.com/business/support/index?page=content&id=HOWTO27289&actp=search&viewlocale=en_US&searchid=1292606819209