ipm_InitResponseSend raise IPMEV_ERROR

Hi,

I used this function to send initResponse

bool
InitResponseSend ()
{
IPM_INIT_RESPONSE initResp;
IPM_NBUP_INIT_RESPONSE nbupResp;
// Initialize the main structure
INIT_IPM_INIT_RESPONSE (&initResp);
initResp.eProtocol = RTP_PROTOCOL_NBUP;
initResp.data.pNBUP = &nbupResp;
// Initialize the NBUP specific structure with an ACK response
INIT_IPM_NBUP_INIT_RESPONSE (&nbupResp);
nbupResp.eResponse = NBUP_INIT_RESPONSE_ACK;
printf("Calling ipm_InitResonseSend()\n");
if (ipm_InitResponseSend (g_hIPM, &initResp) == -1)
{
printf ("ipm_InitResponseSend failed\n");
return false;
}
return true;
}

Almost I received 

IPMEV_INIT_COMPLETE

But some times I received 

IPMEV_ERROR because 

EIPM_BADPARM
Invalid parameter

I don't know why? Please help me how to fix this