Hi,
Is/was there any other Antivirus protection installed than the SEP Client ? (Norton,...)
If Norton, you might want to try the removal tool (https://www-secure.symantec.com/norton-support/jsp/help-solutions.jsp?docid=20080710133834EN&lg=english&ct=united+states&product=home&version=1&pvid=f-home&entsrc=redirect_pubweb) and then check how the virus scan behave.
If you have the following error:
"Symantec AntiVirus has stopped working. A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available."
The following article might help you, which is specific to your SEP version:
http://www.symantec.com/docs/TECH132902
Or, you might try to repair, or simply reinstall SEP.
Keep us inform.
Shulk.