You have Symantec Endpoint Protection MR4 MP1 with Network Threat Protection installed. If you launch an executable from a UNC path on a client, the client loses network connectivity.
When an executable is launched from a UNC path, Network Threat Protection stops responding and no longer allows traffic to pass.
Symantec has removed the download for MR4 MP1 and does not recommend migrating to it until a fixed build is released.
The following workarounds are available: