My Google toolbar offers "WinMX help" as a popular subject.

Wiki also appears to have some discussion about a recent change in program ver, and there are a couple of "our magic plugin gets you back on line" near the top when I search just for WinMX.

It's not a program I've looked at though.

Disabling the firewall doesn't necessarily open all ports, since some of them arent' used except for special purposes; and it may be that the one the program needs is just one that's turned off. The easiest way to open a less used one may be with the firewall on (to access the controls) and poke in an "ok to open" for the specific port needed - but I'm just guessing.

John