Comment 2 for bug 151849

I finally got the flashplugin-nonfree to work, with audio, in Firefox64 on Ubuntu64 Gutsy. I had to resort to installing and configuring PulseAudio and a somewhat kludgy PulseAUdio 'libflashsupport' package, and also involving copying a missing dependency from, a feisty32 system with libasyncns0 installed from /usr/lib/ libasyncns.so.0.0.0 to my Ubuntu64 box /usr/lib32/libasyncns.so.0.0.0 and making a symlink to it to /usr/lib32/libasyncns.so.0.

See thread:

Gutsy64 Flash9 on Firefox64 with sound, Finally! With PulseAudio!!!
http://ubuntuforums.org/showthread.php?t=617142

I don't know as I call it 'solved' but, for myself, it is at least somewhat 'triaged' and is working nicely now.
It works in Swiftweasel now , too.