Iphone 3Gs, 5.1.1, Audio Problem

I’m testing my game on iphone 3gs (ios 5.1.1) and having a problem with audio resuming. After manually suspending/resuming my game works fine and background music is resuming. But after receiving incoming call my game can’t to resume playing music. Btw all sound effects are working fine. I can resume playing music only by manually tapping on sound button in menu. I’m getting trouble with this only on iphone 3gs (ios 5.1.1), iphone 4s (ios 6.1) doesn’t have this problem. In concole output I can see only this:
 

Mar 12 17:19:53 iPhone3gs UIKitApplication:com.vasya.mygame[0x4594][24124] : AudioStreamBasicDescription: 2 ch, 11025 Hz, ‘lpcm’ (0x00000C2C) 8.24-bit little-endian signed integer, deinterleaved

 
Does anyone have the same problem? And is there any solution for this?