There is a good chance you have a variant of Trojan.Bredolab.
http://www.symantec.com/security_response/writeup.jsp?docid=2009-052907-2436-99
As BNH stated, submit the files to Symantec, so that new definitions can be written.
You never stated what version of SAV you are running. If it is SAV 9 or earlier, then you are not getting new definitions to stay protected.
Symantec Antivirus 8.0 reached its End of Support Life as of November 30, 2005 and Symantec Antivirus 8.1 reached its End of Support Life as of January 31, 2007, as defined in the Symantec Enterprise Technical Support Policy. Therefore virus definition updates are no longer supported for this product.
Symantec Antivirus 9.x will reach its End of Standard Support as of March 31, 2009. Virus definition updates for version 9.x will be discontinued on April 1, 2009. Please contact your account manager or reseller for information about our current shipping versions.