I have the same problem too.
The installer says it completed succesfully, and then it launches Firefox to confirm that I got the latest version of the player (it fails to launch IE 9, instead it launches Firefox, maybe because is my default browser, but it should'nt).
Thanks for any help or support.
What is your browser & version?
I'm running Internet Explore 9, 64 bit edition, and I'm using Windows 7 Home Premium 64 bit.
It's working now, maybe I just needed to restart Windows, because I tried again today and now it worked!!
The only issue was that when it completed the installation it launches Firefox with a page saying "Installation successful", instead of launching IE.
Thanks, those links narrowed down my search and the problem is fixed.