YouTube videos don't play in Plurk window

I'm trying to determine if this is a problem with my computer, browser(s), flash or Plurk. When I click on embedded YouTube videos in Plurk, the window opens, but all I see is a white screen. The video never starts playing. This was working earlier this morning. Flash player is running, though, because I can right click the Plurk window and see flash menu. If I visit the YouTube page through the link, the video plays fine and embedding is enabled. Is there a problem with YouTube embedding in Plurk? I've tried this on multiple browsers on this same machine and see the same issue with every browser.