This might help you KB. 
 
Follow these instructions to remove and reset the plugins:
-  Close Firefox
-  Navigate to C:\Program Files\Mozilla Firefox\Plugins\
-  Delete all of the npqtplugin.dll files: npqtplugin.dll, npqtplugin2.dll, etc.
-  Navigate to C:\Program Files\Quicktime\Plugins\
-  Delete all of the npqtplugin.dll files
-  Reset your Quicktime mime settings
And if your MIME setting are giving you trouble (I'll assume you haven't already looked at something for those 

) then try these settings:
Quicktime 7 and Alternative 1.5
-  Close all instances of Firefox
-  Go to Start > Control Panel > Quicktime 7
-  Go to the Audio Tab
-  If using Alternative, select "General Midi" under "Music Synthesizer"
-  Go to the Browser tab and click "Mime Settings"
-  Enable the file types you wish Quicktime to handle. Do not enable Flash.
-  Click OK
-  Go to the Streaming tab
-  Choose the connection that best matches your current Internet connection speed
-  Click OK
Taken from <a href="http://forums.mozillazine.org/viewtopic.php?t=206210">here</a>.