mplayer -ao nas fails: Unlocking unlocked mutex

[Aleksey Cheusov <cheusov%tut.by@localhost>]

'mplayer -ao nas' and libao-based applications like mpg321 and ogg123
fail with the same error message on NetBSD-4.

  mplayer: Error detected by libpthread: Unlocking unlocked mutex.
  Detected by file "/srv/src/lib/libpthread/pthread_mutex.c", line 363, 
function "pthread_mutex_unlock".
  See pthread(3) for information.

or

  ogg123: Error detected by libpthread: Unlocking unlocked mutex.
  Detected by file "/srv/src/lib/libpthread/pthread_mutex.c", line 363, 
function "pthread_mutex_unlock".
  See pthread(3) for information.

Can anybody familiar with NAS and/or libaa take a look to this
problem?  Long ago mplayer forked libao, now they seem mostly
incompatible but may still share the same code.

-- 
Best regards, Aleksey Cheusov.