NPE in custom RPC plugin

we developed rpc plugin as type two and created soap client using axis-1_4.
i am getting following error while accessing SoapMethods through client

AxisFault
 faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException
 faultSubcode: 
 faultString: com.atlassian.util.concurrent.LazyReference$InitializationException: java.lang.NullPointerException
 faultActor: 
 faultNode: 
 faultDetail: 
	{}faultData:null
	{http://xml.apache.org/axis/}hostname:tcg783lt-01

com.atlassian.util.concurrent.LazyReference$InitializationException: java.lang.NullPointerException
	at org.apache.axis.message.SOAPFaultBuilder.createFault(SOAPFaultBuilder.java:222)
	at org.apache.axis.message.SOAPFaultBuilder.endElement(SOAPFaultBuilder.java:129)
	at org.apache.axis.encoding.DeserializationContext.endElement(DeserializationContext.java:1087)
	at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
	at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanEndElement(Unknown Source)
	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
	at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
	at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
	at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
	at org.apache.xerces.jaxp.SAXParserImpl.parse(Unknown Source)
	at org.apache.axis.encoding.DeserializationContext.parse(DeserializationContext.java:227)
	at org.apache.axis.SOAPPart.getAsSOAPEnvelope(SOAPPart.java:696)
	at org.apache.axis.Message.getSOAPEnvelope(Message.java:435)
	at org.apache.axis.handlers.soap.MustUnderstandChecker.invoke(MustUnderstandChecker.java:62)
	at org.apache.axis.client.AxisClient.invoke(AxisClient.java:206)
	at org.apache.axis.client.Call.invokeEngine(Call.java:2784)
	at org.apache.axis.client.Call.invoke(Call.java:2767)
	at org.apache.axis.client.Call.invoke(Call.java:2443)
	at org.apache.axis.client.Call.invoke(Call.java:2366)
	at org.apache.axis.client.Call.invoke(Call.java:1812)
	at localhost.rpc.soap.motMigJiraSoapServ.MotMigJiraSoapServSoapBindingStub.migIsWatching(MotMigJiraSoapServSoapBindingStub.java:1048)
	at com.moto.jira.soapclient.Test.main(Test.java:76)

It was working good in jira 5.0-beta1 version