Hi Padmanabhan,
The error occurs when the web service doesn’t return the expected output structure. It can be a null value a missing xml tag.
If you are calling a web service based on a flow of the Integration server, try running the flow with the validate output check enabled and using the same input parameters.
Also, if you change the input/output on the designer of the flow, you must regenerate the web service proxy and publish again.
#webMethods-BPMS#webMethods#BPM