Hi K,
Here is where I would begin: Best practices for troubleshooting viruses on a network (http://www.symantec.com/docs/TECH122466)
I also recommend running the SEP Support Tool for Load Point analysis - that will identify any suspicious files.
Please supply details on the computer, the version of SAV or SEP, the submission number, etc... with those in hand the forum community should be better able to assist.
Thanks and best regards,
Mick