well its supposed to be, that if you install Quicktime AFTER firefox is installed, quicktime will automatically install the plugins for firefox.
if you put your quicktime on first, you could try reinstalling it (i wouldnt think you'd have to uninstall, just install it again over the one of you have)
BTW, on the earlier subject of offering quicktime without being packaged with itunes. aparently they do.
http://www.apple.com/quicktime/download/standalone.html
Quicktime 7 by itself.