There is a null pointer bug that causes problems for some apps using libao in conjunction with pulse-audio. It was requested I open a separate bug for this: http://bugs.gentoo.org/show_bug.cgi?id=324265
Created attachment 240039 [details, diff] libao-1.0.0 Pulse Audio Fix patch from upstream
+*libao-1.0.0-r1 (26 Jul 2010) + + 26 Jul 2010; Samuli Suominen <ssuominen@gentoo.org> + +libao-1.0.0-r1.ebuild, +files/libao-1.0.0-pulseaudio.patch: + Fix pulseaudio module wrt #329737 by Reuben Martin. Remove -O20 from + upstream default CFLAGS.