For those having problems with flash plugin in firefox on arch linux, more properly, not being able to click the controls in a video in youtube, one of this actons solved it (I don’t know which one because I applied both of them):
adding
export GDK_NATIVE_WINDOWS=1
to /etc/profile.d/mozilla-common.sh
in http://bbs.archlinux.org/viewtopic.php?pid=666490#p666490
installing gstreamer plugins
pacman -S gstreamer0.10-plugins
in http://bbs.archlinux.org/viewtopic.php?pid=669238#p669238
Thanks for the solution. The first one works for me