Netflix won't play on Lion

I recently got the new version of Lion, and after I was done experimenting with it, I decided to go to Netflix. There, I discovered I couldn't play Netflix movies on Safari OR Firefox. The error message I got was this:

Digital Rights Management (DRM) Error

Error code: N8151

We're sorry, but there is a problem playing protected (DRM) content on your system.

Then it showed how to resolve the problem (Shutting out of browser and trying again).

Before, I could play it on my old operating system, Snow Leopard. Was it the change of my operating system that made this problem happen, and how can I fix it?

Thanks!