You know Ian, I have spent days trying to troubleshoot Firefox plugin missing problems... in fact, when we first started embedding WMV files here for Kirk's lessons, I had a hell of a time trying to get it to work in all versions of Firefox... turns out it was the embedding (site side) that was the problem... So you may be wasting your time trying to install the missing plugin. It may be the code at Wholenote that isn't correct.
It might be worth starting a thread over at WholeNote asking if other members are having the same problem with your version of Firefox... or you could save yourself the aggravation and just use IE... you know, it won't kill ya.
Clancy
"I like work: it fascinates me. I can sit and look at it for hours". Jerome K. Jerome