Hi,
This mostly happens if the virus definitions get corrupt.
You can follow the below mentione steps.
1] Un-install SEP from add/remove program.
2] Delete all the symantec folder.
- c:\Program Files\Symantec\
- c:\Program Files\Common Files\Symantec Shared
- c:\Documents and Settings\All Users\Application Data\Symantec
3] Re-isntall the client as un-managed client. Then make is managed.
this should solve your problem if not then.
Run cleanwip & Re-isntall the client.