If you are on a Mac and are having problems with the videos, try Google Chrome with the Flip4Mac plugin . That combination is working in MAC OS 10.6.8 (Snow Leopard).
UPDATE: Lion was previously reported to be unable to play Windows Media at all. A report here: https://discussions.apple.com/message/17001136#17001136, states that it will work with QuickTime Player 7.6.6 and Flip4Mac. If you try this please report back and let us know the results.
If you are on a PC and are seeing funkiness in the video, like a black screen or weird flickering, weird positioning, please make sure that both your browser and Windows Media Player are up to date. If you still have problems, please post a comment here with as much information (including version numbers) as you can provide about your Operating System, Browser and Windows Media Player, and we’ll look into it.