Symantec AntiVirus cannot detect viruses after you install a hotfix
Symantec AntiVirus cannot detect viruses after you install a hotfix on a computer that is running Windows Server 2003 or Windows XP SP2
You install a hotfix on Microsoft Windows Server 2003 or on Microsoft Windows XP Service Pack 2 (SP2). However, after you install the hotfix, Symantec AntiVirus cannot correctly detect viruses in encrypted files that reside on a network share or in a document library.
This problem occurs if you have installed the hotfix that is described in the following Microsoft Knowledge Base article:
922582 (http://support.microsoft.com/kb/922582/) Error message when you try to update a Microsoft Windows-based computer: "0x80070002"
This problem occurs if the following conditions are true:
• A legacy filesytem filter driver is installed on the same computer as Symantec AntiVirus.
• The legacy filesystem filter driver is configured to encrypt files that are stored on network shares.
http://support.microsoft.com/default.aspx?scid=kb;en-us;933215
http://support.microsoft.com/kb/922582/