Communication Soap to java proxy error

Hi,

I have a scenario SOAP --> PI --> Java Proxy by http destination (in PI 7.31)

The problem is when I test with soapui, I have this error iin soapui and in the channel sender and receiver (the same error):

SOAP: call failed com.sap.engine.interfaces.messaging.api.exception.MessagingException:
com.sap.aii.af.sdk.xi.srt.BubbleException: HTTP Response Received. Status Code = 500 [null "null"]

where can is the problem? I have othe scenario similiar and it's working fine..

Thanks and best regards

Mónica