Ugh! How do I install this plug-in?

I’m trying to watch a video online (through ABC.com), it makes me install a new video player (Move Media), but nothing happens at the end (it should start playback automatically), and when I return to the page it asks me to install again. I’ve restarted my browser, and I’ve checked and do find the video player in my internet plug-ins folder. I tried to open it, but it asks what application to open it with. Ideas?

MacBook, Firefox. Also tried Safari.

Thanks!