If Youtube videos do not play reload the page, that's a Youtube bug.
Or maybe now, a few years later, it's a new bug ;-)

Digitonal - 93 Years On

Honeyroot - It's All Good

Marconi Union - Flying (In Crimson Skies)

Regina Spektor - Don't Leave Me (Ne Me Quitte Pas)

Systema Solar - Malpalpitando