I was frustrated to find that, upon installing QuickTime 6, flash-based web content loaded into Mozilla was suddenly being handled by QuickTime instead of the preferred Flash 6 player. IE was not affected in this manner. Well, here's the deal....
Handling of MIME types in Mozilla has been left to individual applications. Which is to say there is no pref for customizing these options. Further, if multiple plug-ins are installed to handle a given content type, the one that "wins" is the one whose plug-in file in /Library/Internet Plugins comes first alphabetically. Users are empowered to take control of which plug-in they use by their renaming plug-ins.
So I renamed the QT6 plugin (by putting a "z" at the front of its name), and, bingo!, it works (and IE is unaffected by the name change). I hope QuickTime doesn't get flak for Mozilla/NS6's bizarre handling of plugins.
[Editor's note: Running version 1.0 of Mozilla, I visited Macromedia's Flash pages, and everything seemed normal - Flash content displayed within the browser window and without any obvious signs that QuickTime 6 might have been in control ... and my /Library/Internet Plugins folder still has QuickTime listed above the Flash/Shockwave plugin. I'm not sure why I'm not affected here while hoopyfrood is, but thought others might find this tip useful if they're having a problem with QuickTime and Mozilla.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002071909090421