Mozilla Firefox ActiveX error

Source

a. Close all Firefox instances
b. Search for npmozax.exe [this is the plug-in I downloaded earlier today after which my Firefox went out of control]
c. Delete npmozax.exe
d. Search for npmozax.dll
e. Delete npmozax.dll
c:\program files\Mozilla firefox\plugins and delete npmozax.dll

I had the same problem and its due to the plugin for Quality Mercury Center.
I disabled this plug in to get rid of the error message, but how do you access Quality Mercury Center now? The plug in was required to access this program...
1. Click here to download Netscape 6 / Mozilla ActiveX plug-in (self-extract file)
2. Unzip downloaded plug-in into browser plug-in directory.
3. Restart the browser.

Source

These are the Media Player plugin files you should see in your plugins folder, which is located here: C:\Program Files\Mozilla Firefox\plugins

Windows Media Player 9
npwmsdrm.dll
npdrmv2.dll
npdsplay.dll

ActiveX
npmozax.dll

Real Player Version 10.5
nppl3260.dll
nprjplug.dll
nprpjplug.dll

QuickTime Version 6.5.2
npqtplugin.dll
nsIQTScriptablePlugin.xpt
QuickTimePlugin.class

If you don't see similar files like the above in the plugin folders, then copy them from the Media Player Program folders.

When you install a player, you can test it on various files here:
Media Test Pages
Audio, Video, & QuickTime Movies

cebaehren's solution:
Mediaplayerconnectivity

Allow you to launch embed video of website in an external application
with a simple click rn
* Replace the stream by a simple button
* Add a download icon in the status bar
* And/Or add links to right click
* Works with RealMedia, QuickTime, WindowsMedia, Playlists, Flash, background sounds, Nullsoft video, Shockwave
* Allow the use of any capable media player (with command line support)
* Support Media Metafiles (ram, rpm, wmv, wm, wma, asx, asf, ...)
* Activable per media format
* AutoPlay feature : automaticatlly start to play the first media
* Configuration wizard
* SmartPlay : automatically search and choose the best source using metafile ('+' icon) if exist
* List all media links on the webpage
* Use a sidebar for lists
* Multilingual rnrnNote : for OSX users, please use v0.5.6 available with
'Version History' link (on left) or from my website, versions 0.6+
don't works fine with OSX (I don't have a Mac for my tests....).