Lets assume its not because you live in North Korea or China ..
I think you probably have two filters going at the same youtube link. When this happens filter a, turns a YouTube link into "something." And then filter B comes alongs and turns "something" into "something else."
This is a bit unusual because generally only the multimedia plugins filter handles YouTube links. Although my own video filter VideoEasy can too. I wonder by chance, do you have that installed? Generico is less likely to be the culprit here because it only filters on the funny looking Generico strings, ie not YouTube links.
Try turning off all the filters you have one by one, and just leave the Generico one in place. If it sputters into life you will know that the filter you turned off (or the generico one) were interfering with things.