I was watching an episode of Community recently when the podcast error window popped up. I couldn't exit out of it so I waited for the timer to count down to 0, but when it did, another file failed and the window stayed up. The counter never restarted and I couldn't close the window manually or access the player controls directly.
I managed to pause the video by pressing the Start Menu button (thus bringing up the task bar) and pausing the video through the Media Monkey tray icon. Here's a screenshot:
I also noticed the files that failed were mp4 files which Media Monkey supports.
