It was my understanding that the only difference between Virtual Server and Port Forwarding is that you can do a range of ports with Port Forwarding whereas you cannot with Virtual Server? I'll give it a shot anyway when I get home, but if it works, then it would lead me to believe that there is still an issue with Port Forwarding.
I am able to telnet to the server, but I do not remember when I tried if I'd already performed my work around or not.
If Ventrilo uses UPNP, is it possible that Ventrilo is trying to configure the port (which you manually configured) via UPNP? If so, I'd prefer to disable UPNP support in Ventrilo since UPNP port openings are harder to see and harder to persist.
What is the work-around?
Finally, before and after the port-forwarding stops, take a look at your Status - Internet Sessions screen. You should see:
192.168.0.199:3784 77.66.55.44:3784 *.*.*.*:* UDP - - 128 -
192.168.0.199:3784 77.66.55.44:3784 *.*.*.*:* TCP - - 128 -
or maybe -- not sure which would be right
192.168.0.199:3784 77.66.55.44:3784 *.*.*.*:* * - - 128 -
(where 192.168 is your LAN machine and 77.66. is your WAN port)