Playback function only run once?

Hi, I met a very wield issue in Asterisk 1.8/1.8.1. When I made a auto dial-out file as follows

Channel: Mobile/NOKIAE72/0*****
Application: Playback
Data: hello-world which will play a hello-word.gsm file.

I found this .call file will work only once(I can heard the “hello world” voice). If i cp the .call file again, the E72 will dial number ,but I can not heard any voice more. I need to restart asterisk service ,so it can work.

Can anyone give me a hint about this?thanks