I can't reproduce this consistently, but I've seen it a few times since I've turned on plugins.click_to_play. I'm using Aurora by the way. Sometimes when loading flash videos, such as on youtube, there will be no video displayed, but audio will play. Sorry I can't give you more info here, it seems to happen randomly and when you reload the page it works the next time with both video and audio. There's a definite correlation with click_to_play because I've never seen the issue before and haven't changed my flash version (11.3).