Argh! Something went wrong and a serious error occurred:

Your GStreamer installation is missing a plug-in.

gstdecodebin.c(1668): gst_decode_bin_change_state (): /timeline/playbackbin/Instrument_0/gnlcomposition0/Event_2/internal-decodebin

It is recommended that you report this to the Jokosher developers or get help at http://www.jokosher.org/forums/