I get that same error. It's because I refuse to install Flash player on this computer. (Makes every browser unstable)
The only videos that work without Flash Player are ones from Youtube that work on the HTML5 codec instead of Adobe's Flash Rubbish.
IE Does not properly support HTML5. (Or any web standards) Firefox Does support HTML5 Video, in a limited form (It's what I use)
You should be able to play the videos in Chrome though, as it has it's own inbuilt Flash compatibility. but Chrome is rubbish on RAM usage, and crashes constantly on low ram machines with more than a few tabs open. (Low is 6GiB or less)
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Looks like recently the Video Player on here was changed from JWPlayer (Which required Flash) to some other HTML5 compliant Video player (Or was Updated to a new version of JWPlayer) (As i can actually see previews for once!)
Try Firefox or Chrome. see if that makes any difference.