With Symantec Endpoint Protection (SEP) Antivirus component 12.1 installed, a piece of software that performs very repetitive network file access is slower to start or to work with.
The Auto Protect Network Trust feature within SEP adds two registry keys that disables a part of the SMB2 Client Redirector Cache. The keys are necessary for reliable operation of the trust feature, but can be removed if trust is not used (or if network scanning is disabled altogether).
For further details about the SMB2 Client Redirector Cache please see:
http://technet.microsoft.com/en-us/library/ff686200%28v=ws.10%29.aspx