Proxomitron Won't Allow YouTube

[wingspar]

All of a sudden, yesterday I could no longer look at videos at YouTube. I updated to the latest flash player, even deleting the old one, still no video. Finally, after just about giving up, at the suggestion of someone to disable popup blockers, I disabled Proxomitron. Bingo. I can watch videos on YouTube.

Why would Proxomitron all of a sudden prevent me from watching videos at YouTube? Did YouTube make a change that conflicts with Proxomitron?