As of this morning, most YouTube videos are not playing. After the advertisement (which always plays properly), the player goes black with no controls. Right-clicking shows "Movie not loaded".
This happens in both IE10 and Chrome on Windows 7 64-bit (I'm using 32-bit browsers.)
I have followed the instructions in several other threads here. Flash has been uninstalled completely and reinstalled. (Current version 11.8.800.168). Browser, Flash, and Macromedia caches have all been deleted and hardware acceleration disabled. Add-ons/plug-ins/Active X have been variously disabled and enabled. The https hack likewise does nothing.
What is going on?