Programmer and network is totally different field,
Maybe you can ask your husband to give it a try.
I am networking specialist, and I am not good with programming BUT, I am good at Networking.
What you see black screen meaning the router OR modem is blocking the traffic flowing to the VP which ultimate result black screen. It is no question about it. What really happened is that the router inside is like a security guard and if the traffic coming in does not please the security guard, it will block them. You need to go in router and/or modem and tell Security guard to BACK OFF and let them going though which means enable the DMZ or port forwarding rules. Some modems use Static-NAT, pinhole, and others use IP-passthough which turns the DSL modem into dummy modem and pass everything though to router. These terms I just mentioned really means same thing.
Once you set it up right then you won't have problem with black screen, I can bet you a million dollars on that one. If he does not believe me, then you can continue to have problems which I can easily bet on.
BTW, somebody said that Port forward is better than DMZ which is true on most cases. Reality, DMZ is easiest way and fastest to set up than port forwarding. BUT the reason why port forwarding is better is because whenever the router or modem reset, or upgrade with new software it will not interfere the port forwarding setting. On other hand will disable DMZ and requires re-set up.
It IS possible to have two routers however need to set it up right in order for them to work right, otherwise it will never cooperate with each other.
Two routers is really like having two steering wheels with two drivers in same car, will the car go smoothly? You can decide.
I don't believe what the tech supports gave me many different stories. They asked me for IP Address to check it out. I has double router together. My husband didn't want to remove the double D Link routers. He didn't believe what the tech support told me to do. My husband switched the router to airport express from d link. Now it's not work. I told him to get back to D-Link router back. He put a double router since the deaf installer came to my apt to hook up my new vp 200 last year ago. I do have problem with black video many times. I am frustrated with tech support and my fiance between. I gave it up their help. My husband is not allow me to let installer come to repair my vp. Because my husband is a computer programmer. He is a GEEK!!! He is a brag about everything. He don't trust any tech support about my our IP address. I don't know to do. I just tired of dealing with over tech support situation! (sighing)