I can't get YouTube to play any HD videos in Safari. Works fine in Chrome, Firefox, etc. In safari, it won't select it automatically. When I do it manually, the video goes blank and doesn't play. This has been happening since before I installed Mavericks, so its not the issue. Actually.. I was kind of hopping it would resolve the issue. Anybody else having this problem, and know of a way to fix? Everything is up to date. Edit: 2012 Air if that matters. Nevermind. Literally right after I posted this thread it ended up working. I have no idea what the problem was.