version is cooking, current upgrades (unrebooted)

Verify your version of sox is 14.3.1
The stable version of sox 14.3.0 is compiled against stable ffmpeg which provides libavutil.so.49
The cooking version of sox 14.3.1 is compiled against libavutil.so.50 which is what your linking to.
You have glibc-dev installed and run ldconfig as root after creating links to library's ?
Verify all deps to shared objects:

ldd path.to.executable

still demands 49.

sox-14.3.1
glibc-dev-2.11.2

cp -s /usr/lib/libavutil.so.50 /usr/lib/libavutil.so.49

ldd /usr/lib/libavutil.so.49
linux-gate.so.1 => (0xffffe000)
libm.so.6 => /lib/libm.so.6 (0xb77f8000)
libpthread.so.0 => /lib/libpthread.so.0 (0xb77e0000)
libc.so.6 => /lib/libc.so.6 (0xb7697000)
/lib/ld-linux.so.2 (0xb782d000)

root@slitaz:~# ldd /usr/lib/libsox.so.1
/usr/lib/libsox.so.1: /usr/lib/libavutil.so.49: version `LIBAVUTIL_49' not found (required by /usr/lib/libsox.so.1)
linux-gate.so.1 => (0xffffe000)
libltdl.so.7 => /usr/lib/libltdl.so.7 (0xb76d0000)
libpng12.so.0 => /usr/lib/libpng12.so.0 (0xb76ab000)
libmagic.so.1 => /usr/lib/libmagic.so.1 (0xb768f000)
libgomp.so.1 => /usr/lib/libgomp.so.1 (0xb7683000)
libasound.so.2 => /usr/lib/libasound.so.2 (0xb75b7000)
librt.so.1 => /lib/librt.so.1 (0xb75af000)
libao.so.2 => /usr/lib/libao.so.2 (0xb75ab000)
libpthread.so.0 => /lib/libpthread.so.0 (0xb7593000)
libdl.so.2 => /lib/libdl.so.2 (0xb758f000)
libavformat.so.52 => /usr/lib/libavformat.so.52 (0xb74f0000)
libavcodec.so.52 => /usr/lib/libavcodec.so.52 (0xb6dc1000)
libavutil.so.49 => /usr/lib/libavutil.so.49 (0xb6db6000)
libmad.so.0 => /usr/lib/libmad.so.0 (0xb6da0000)
libid3tag.so.0 => /usr/lib/libid3tag.so.0 (0xb6d8e000)
libz.so.1 => /usr/lib/libz.so.1 (0xb6d77000)
libvorbisfile.so.3 => /usr/lib/libvorbisfile.so.3 (0xb6d6e000)
libsndfile.so.1 => /usr/lib/libsndfile.so.1 (0xb6d09000)
libFLAC.so.8 => /usr/lib/libFLAC.so.8 (0xb6cb7000)
libvorbisenc.so.2 => /usr/lib/libvorbisenc.so.2 (0xb6b40000)
libvorbis.so.0 => /usr/lib/libvorbis.so.0 (0xb6b18000)
libogg.so.0 => /usr/lib/libogg.so.0 (0xb6b12000)
libmp3lame.so.0 => /usr/lib/libmp3lame.so.0 (0xb6a92000)
libm.so.6 => /lib/libm.so.6 (0xb6a6a000)
libc.so.6 => /lib/libc.so.6 (0xb6921000)
/lib/ld-linux.so.2 (0xb7770000)


tux@slitaz:~$ sox
sox: /usr/lib/libavutil.so.49: version `LIBAVUTIL_49' not found (required by /usr/lib/libsox.so.1)