YouTube videos not playing or converting with most tools

[Parakommando]

In the past I never had a problem playing back YouTube videos on my desktop (I have Perian installed). But ATM that isn't working. So okay, I can use on-line conversion tools like Vixy or Media Converter. But for some videos even they won't work. Fortunately a site called CatchYouTube.com does work - so far. Why is that? Does anyone else have these issues? It's very odd.

[El Capitan]

http://www.zamzar.com/

[Faceman]

DownloadHelper for Firefox to grab the FLV

Media Player Classic Home Cinema - http://mpc-hc.sourceforge.net/ to view on your comp

To convert: http://www.erightsoft.com/SUPER.html