If you are finding your systems are infected there are a few utilities you can run.
I would start with downloading the latest Rapid Release definitions.
One you have the new defs, boot into safe mode and running a Disk Cleanup (right-click the C drive, Properties, Disk Cleanup) - that will delete all the files that are in these temporary locations, as well as IE's temporary files, etc. Perform a full system scan in safe mode.
If that fails to detect and remove the threats, try running the Power Eraser tool. The Power Eraser Tool eliminates deeply embedded and difficult to remove threats that traditional virus scanning doesn't always detect.
Power Eraser tool –
http://security.symantec.com/nbrt/npe.asp?lcid=1033&origin=default
You can also run the Load Point Anaylsis Tool, this is found in the SEP support tool.
How to use the Load Point Analysis within the Symantec Support Tool to help locate suspicious files http://www.symantec.com/business/support/index?page=content&id=TECH141402
Rapid Release Virus Definitions –
http://www.symantec.com/business/security_response/definitions/download/detail.jsp?gid=rr
Keep us posted on your situation.