As far as I can tell, its not a quicktime plug-in you need, its some sort of Microsoft activeMovie 2.0 codec -- I'd try either a)reinstalling IE or some older version of Netscape, cuz Netscape 6 is buggy or b)try finding the Active Movie codec on microsofts site. Wish i could help more, but i never quite figured out how netscape 6 can be configured to auto-download plugins.
-Ed