Hulu Error Code 3322, streaming slows elsewhere

When I try to watch a video on Hulu I get the following error message: "There was a problem playing this protected content (Error Code: 3322)". Also, when I watch full episodes on www.fox.com the video starts to slow about halfway into the episode and continues to get slower as the episode progresses; the image is very slow by the end of the episode and out of sync with the sound. I've tried clearing my Flash cache, resetting license files, and other common suggestions. My Flash version is 19.0.0.226, my browser is Firefox (NPAPI), and my OS is Windows 7. (Note: I was able to watch an episode found on Hulu via Google Chrome without any problems, but I'd like to fix whatever is causing the problem on Firefox.)