Please, look for any mp3 decoder library on your rootfs:
You should have lib_omx_mp3_dec_v2_arm12_elinux.so, for example.
so, type find -name *mp3* and see what you have. (without a decoder you will never get it decoded, let´s eliminate this at first)
Other thing, find -name component_register
component_register is a text file that will tell you which are the mp3 decoder and where it´s from. Please let me know if there is any mp3 reference.
Do you get the error during Music opening? Or it´s when playing some music?
Can you see any music?
Do you have any SDCard in?