Please see the attached document for the steps to download the latest Symantec Endpoint Protection. This will fix the known issues with Symantec and SigmaXL where Excel hangs on exit. Your Symantec Endpoint version should have the version number 11.0.6300.803 after the update.
This is the note from Symantec on their website:
Use the link below to view instructions on upgrading your Symantec Antivirus.
http://www.sigmaxl.com/images/How to Update Symantec.pdf