How would you configure ports and IPs for FMS 4.5 to allow RTMFP streaming across the Internet?

Basically I've got an AS3 app set up that allows video chats between n number of parties, using RTMFP.  The problem is that when I tried to connect a computer from across the Internet, as opposed to our intranet, suddenly it couldn't connect at all to RTMFP for that app (though it was able to succeed in using an RTMP fallback that was in there).

So after hunting around, I got the network administrator to supposedly open up 1935-1960 UDP for outbound traffic on the external IP for the FMS's server (same server as the AS3 app), and he apparently opened them up for inbound traffic as well.  I also went into Adaptor.xml and changed this element:

<HostPort>:19350-19360</HostPort> 

to say this:

<HostPort public="XX.XX.XXX.XXX:19350-19360">:19350-19360</HostPort> 

where XX.XX.XXX.XXX is the external IP for that computer.  At this point in time though, even though computers across the Internet are able to connect through RTMFP, the video/audio streams aren't getting through at all across the Internet.  What's more is that even on our intranet, there are one-way versions of that problem now.

Network administration is not my strong suit, in all honesty.  Where would I need to start looking in order to solve this problem?  Thanks!