Default "Couldn't prepare Instant Mix. Please try again" - Ok Google

Hi everybody!
I'm playing today with the Ok Google commands. I can launch apps and search information, but when I tried to listen any song Google Play Music send me back that message. I can't create any Instant Mix on the app either. I'm on stock 4.4.2 with ART enabled. Hope anyone can help me and thank you all!

EDIT: I solved it uploading all my music and erasing the music I had on the sdcard
== MOBILE ==
Nexus 5 on Stock 4.4.2 KOT49H

== DESKTOP ==
Intel i7 920 @ 3.20Ghz
6GB DDR3 @ 1600Mhz
SSD OCZ 60GB FORCE 2
HDD WD 1TB Black Caviar
ATI Radeon HD4890 1GB DDR5