We had an application (Dazzle) on a firewalled Windows 7 computer that was failing due to an unknown error. We’d already whitelisted the domains as suggested by Endicia here . Analyzing the problem, we found connections to se.symcb.com/se.crl and se.symcd.com being blocked.
Investigating this we determined that the domains are owned by Symantec Corporation and are used in the process of verifying secure certificates, more specifically, the ‘Certificate Revocation List’. We found that whenever the program starts, it tries to make this connection. After whitelisting the domains in our local proxy, the program worked normally.