Failed to start billing service.

Question

I am trying to implement billing in an application in my application. I use the code from the sample dungeons.

everything works fine and i can buy. but after I left the application, I got the error message "the application stopped working" and in LogCat I see.

05-10 14: 33: 22.293: E / AndroidRuntime (9568): java.lang.RuntimeException: cannot start the com.package.name.BillingService@2beca0b0 with zero: java.lang.NullPointerException

Does anyone know what might cause this problem?

edit-1: the problem is that the billingService is still active. and onStart is trying to send zero intentions (I can solve this if null == intent, but it is not) I use unbind when I finished the purchase.

thanks.