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>.