Of course you need to allow NextPVR through your firewall for TCP and UDP, there are lots of posts on that. The nonsense is allowing the public network through making a difference. If I am reading you correctly you are wireless and not using WEP 128 which just won't work.
This thread is actually why I don't support the MVP, the tech is too old, yet people expect a lot. There is a reason these were gathering dust for you.