Hi,
Thank you for posting in Symantec community.
Do you get this pop up during Symantec Endpoint Protection (SEP) startup?
Refer this article if it's applicable: SMC.exe crashes with error Event ID 1000 in Application log, relating to dll "spnet.dll".
http://www.symantec.com/docs/TECH105983
SEP 12.1.671.4971 is RTM version, you should upgrade to the latest version i.e SEP 12.1 RU5 (12.1.5337.5000)