I just tried Gnash on my Debian Sid box and Youtube doesn't work. According to the gnash-dev mailing list, Youtube has been using an SWF 10 player since October of last year (http://lists.gnu.org/archive/html/gnash-dev/2009-10/msg00...). If Gnash doesn't properly support SWF 10, why is everyone saying that Youtube works? Am I doing something wrong?