After upgrading to Firefox 22, remote control from ZCM is broken. I get the same result using Firefox in Windows and in Linux. Firefox now doesn't load plugins when the <embed> tag has hidden=true. To work around the problem, I made a quick greasemonkey script that finds the hidden <embed> tag and removes the hidden attribute. Now remote control is working for us again in the latest Firefox. Here is the greasemonkey script I used, replace the https://zcmurl/ with the url to your zcm installation:

// ==UserScript==
// @name        Fix hidden nzrviewer
// @namespace   zenfix
// @include     https://zcmurl/*
// @version     2
// ==/UserScript==

var embeds = document.getElementsByTagName('embed');
for (i=0; i<embeds.length; i++) {