Current audacious-plugins has to be recompiled against libmowgli
 

audacious
Failed to load plugin (/usr/lib/audacious/Transport/gio.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Transport/neon.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Transport/unix-io.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/ladspa.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/echo.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/crystalizer.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/compressor.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/sndstretch.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/voice_removal.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/stereo.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Effect/resample.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/aosd.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/song_change.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/gtkui.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/alarm.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/mtp_up.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/statusicon.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/vfstrace.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/hotkey.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/gnomeshortcuts.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/evdev-plug.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/cd-menu-items.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/skins.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/General/streambrowser.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Visualization/paranormal.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Visualization/blur_scope.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Visualization/spectrum.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Visualization/rocklight.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Container/m3u.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Container/xspf.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Container/pls.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/alsa.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/ESD.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/OSS.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/crossfade.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/filewriter.so): libmowgli.so.1: cannot open shared object file: No such file or directory
Failed to load plugin (/usr/lib/audacious/Output/null.so): libmowgli.so.1: cannot open shared object file: No such file or directory
ALL OUTPUT PLUGINS FAILED TO INITIALIZE.
audacious: unable to launch selected interface skinned

I got the same errors...

This is how i solved the issue->

1. Get the latest 2.4.0 sources (player+plug-ins) from -> http://audacious-media-player.org/
2. Get the slackbuilds from the Slackware DVD (player+plug-ins).
3. Change the Version number.
4. Run and Compile.
5. upgradepkg --install-new *.t?z

6. ENJOY Audacious 2.4.0!

Edit 1. Compile and install the player first and then the plug-ins.