Video does not from from the internet.

I have about 8 computers that now have Windows One Care installed that no
longer play video from the internet, for example video from weather.com.
When I click on the video from the site, the web site tells me that I do not
have a media player installed. I have Media Player 11 installed. I have
uninstall and reinstalled media player with no luck. I am current with all
my updates for XP. Under One Care's firewall settings, I have checked 'Video
- Watch video on the internet.'

Any thoughts?