I am running Vista, and I just downloaded FireFox today only because I had found this AWESOME streaming site which wanted me to use Firefox, and for the movie files it wanted me to download Adobe Flash Player. I knew I already had both Adobe Flash and Adobe Shockwave Player.

I deleted Flash player (by accident) and just for measure I copied my Windows/System32/Adobe Files into my Program Files/Mozilla Folder. I restarted my computer and restarted FireFox set as my default browser.

I went back to that same site and tried to watch a movie, I got the same pop up to download Adobe Flash Player and was once again redirected to the site, I clicked on Install Adobe Flash Player, I got a pop-up window asking me to close Firefox, so I closed everything except the download task, and pressed try again and wallah!! It downloaded!! I went back to my awesome site clicked on a movie and god bless cable internet I was watching a new release movie in no time.

So I would try, using Firefox and not IE anything
Set Firefox as your default browser
Attempt to download Adobe Flash Player
Close any open windows..
If you think it will help, copy any Adobe Flash Player or Shockwave Player files into your Mozilla folder.