Buenas.
He encontrado esto. En esencia tener cada uno en su carpeta. Notificaciones y tonos de llamada. Prueba a ver si se soluciona de este modo compañero

or those of you using custom tones, I had a somewhat similar issue, where my tones were not being found/reconized. For me the solution was to move my ringtones and notifications into folders called ringtones and notifications at the top level of the SD card. Maybe you could try doing the same and see if that works.

/mnt/extSdCard/ringtones
/mnt/extSdCard/notifications

En esta url hablan de ello.

https://code.google.com/p/android/is...tail?id=171382