For the download website to properly detect your BlackBerry device, you should start your Browser and choose Options, then choose Browser Configuation and make sure "BlackBerry" is checked under "Browser Identification". If you have Firefox or another browser selected, the download site will not automatically recognize your phone.
This problem may occur while using Opera as well. Opera does not send a device identifier string to the download site, so the download site cannot detect your device.
Also note that on the BlackBerry Storm, a dialog may popup asking if you want to download the Boopsie Framework. Be sure to highlight Yes before pressing - the highlight sometimes moves around and highlights the wrong choice when you just 'press' vs. highlight and press.