I checked that a WAVE file and an Ogg Vorbis file could play by the USB audio device.
There is a bug in standard MP3 plug-in, and Segmentation fault occurs.
An MP3 file can be played by using media-plugins/xmms-mad-0.5.6-r1 .
stick a fork in it!
Created attachment 47571 [details, diff]
patch for xmms-1.2.10-r5.ebuild
When optimizing more than -O2 on ppc64, Segmentation fault occurs in mpg123
I think that this problem is solved by restriction of optimization level.
patch commited :-)
FYI, This problem recurred.
I applied the same patch to media-plugins/xmms-mpg123 and solved this problem.