I get a message "Pins cannot connect due to not supporting the same transport. (Error=80040266)" since I didn't install WMP 9 or later. In fact I don't use WMP at all so there is likely more stuff that won't work.
My choice.
In your case, you can use IE for CNN but keep in mind that there are no plans to make Mozilla/Firefox to work with all sites.
Bob
my firefox browser couldn't play the video in cnn. why? there's something written on the botton tab, something about the script.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic