KWPro.net

Well, I'm not sure if this is a bug or intentional, but apparently the newer versions of Flash (from 10) no longer automatically installs Flash into the correct Firefox directory if you need it. So you need to manually install the plugin into the correct directory.  Here's the instructions for doing this:

• After downloading the latest Flash plugin, run the "installer."
• The installer will place the plugin files under C:\WINDOWS\system32\Macromedia\Flash
• You will need to copy the files NPSWF32.dll and flashplayer.xpt to C:\Program Files\Mozilla Firefox\plugins
• Restart Firefox

Do this if you're encountering the a Javascript/Flash error on sites like youtube.