I've run into a few problems recently with my PCH and wondered if the problem was related to an recent upgrade Essentials did. I still am not sure but for me, I just changed the port to a different one and it worked. So, if it worked for the new port, why not the old?
For what it's worth, I have my firewall set to enable. I think, but am not sure, that when you install NPVR, it sets the firewall exception.
Custom ASUS P8Z77 V-Deluxe, Core i7 3770k, 16 GB Memory-ASUS ENGTX560 DCII TOP/2DI/1GD5 GeForce GTX 560, H80i Cooler, 750W PS, CM HAF XM RC-922XM-KKN1 case,Corsair GS CSSD-F240GBGS-BK 2.5" 240GB SATA III SSD, InfiniTV4 & HDHomerun Tuners- running Windows 8 (and other goodies)
#2--P877WS- Core i7 3770k, 16GB Memory-GeForce GTX 650Ti, SATA III SSD, H100i cooler, 750W PS, Windows 8.1