Unable to get "watch movies instantly" on Netflix using Safari

Hi, I have a Mac PowerBook running OS X 10.5.8, and I just signed up for Netflix. However after attempting to watch my first movie "instantly" using Safari, the system requirements page came up instead of the movie. After reading the system requirements I have determined I meet all of them (an intel based Mac running OSX 10.4.11 or higher, Safari 3 or higher, and 1 GB of RAM), my internet connection is also fast enough, I'm using a 802.11n wi-fi connection. I contacted Netflix tech support who sent me a download for Microsoft Silverlight, saying that all I needed was the newer version. I downloaded that update, however this had no effect on my problem. Once again the system requirements page came up.

I called Netflix again. The Netfix tech advisor told me that the settings on safari are probably to blame, but they said they did not know the correct settings to make it work. They advised me to contact apple or use another internet browser. I downloaded Firefox 13, however when I tried to open the Firefox application an error message came up, "You can't open this application "firefox" because it is not supported on this arcitecture".

I don't know what my next step should be. Any ideas would be greatly appreciated. Thanks in advance for your help!