Problem with join MP3 Shield and HCSR04

Hello everyone!

I have sparkfun mp3 player shield and hcsr04. I would like to join them in Arduino uno, but i have a problem with that. Simple join Arduino with hcsr works fine. This same situation with mp3 shield (uno +mp3 ok). But when i join Arduino with hcsr and mp3 shield, its not working at all. I am newbie in Arduino projects and i dont now what im doing wrong. Is this a problem with power? Or is it problem with pin reciver and transmitter (pin 11 and 12) in hcsr?

Code is not a problem - this i can do correctly, but join all together is a horror (small skill in that).
Could somebody help me with that?

Regards!