To troubleshoot the failure of the Symantec Endpoint Protection (SEP) client's definitions, it can be helpful to remove potentially corrupted definitions from the client.
The following are instructions for removing corrupt or potentially corrupt definitions from a Windows SEP client. It is important to consider the fact that if you follow this procedure and the definitions are not restored then the Windows SEP client client may be in a worse state (having no definitions) than it was before (where it was only suspected that the definitions were corrupted). Make a copy of any directory or registry contents you plan to delete.
Note: Disable Tamper Protection on the client before executing the following procedure to avoid getting an "Access is denied" error.