Are you guys witnessing the same bug, just a black square on Youtube embedded links ? I thought it was just me with my upgrade to Windows 7 64-bit and 64-bit Chrome + Flash!
Won't be long before they just make breaking Adobe Flash intentional to push the public into phasing it out... Regular MP4 video embedding with HTML5 when it comes to Youtube works fine at present. Like other older forums, ours uses Flash to handle Youtube links so they're all broken now (Confirmed on my Windows 10 tablet, same problem).