Try completely completely uninstalling Flash player and then re-installing it. You can uninstall Flash from 'Add/Remove programs'. (It's listed under 'A' for 'Adobe', rather than 'F' for 'Flash').
Alternatively, try switching browsers. Some Flash sites will load in Internet Explorer but not in Firefox - and vice versa. Firefox should be your default browser (because it's much better than Internet Explorer). If you haven't got it yet, you can find it here:
http://www.mozilla.com/en-US/firefox/
Chris