I believe this is related: http://www.nvnews.net/vbulletin/showpost.php?p=2518770&postcount=104 The problem stems from Flash 11.2 w/ libvdpau: Flash is incorrectly swapping the order of the U and V video planes when calling vdpau. That patch (from an nvidia employee, incidentally) *sortof* fixes it, but it's a pain. There is a lot of discussion on this issue in the ArchLinux forum, including more relevant links and a seeming confirmation that Adobe will not be fixing this. :( https://bbs.archlinux.org/viewtopic.php?pid=1079335 I can confirm that downgrading to adobe-flash-11.1* fixes it. There are security concerns with 11.1, but at least some of the opinions are that those problems were Windows-only, and that 11.1 on Linux is fine. I'll be looking for a response on that question from peeps that know more about that than I do. To help users, another possible YouTube-specific workaround is to enable HTML5 video (http://www.youtube.com/html5) to avoid using Flash at all. Unfortunately, reports are that this only works for some videos - the ones with Advertisements *always* use Flash.
*** This bug has been marked as a duplicate of bug 410435 ***
