BPM error : Message pipeline PE_ADAPTER unknown XML message not found. Help

Hello All,

I have done 3 steps in BPM

RFC --- BPM --- RFC

RECEIVE step ==> Opens SYNCH ASYNCH bridge and receives RFC request message

SEND synchronous ==> to send RFC request and get the RFC response.

SEND ==> Closes SYNCH ASYNCH bridge and Send's response back to the RFC.

In my last send step (response back) I am getting message

"Message pipeline PE_ADAPTER unknown XML message not found" .

Pls help