Oracle application server HTTP error 401 authorization required axis2

I have a jsp application deployed on OAS server 10.1.2.0.2. The problem which I have is that only sometimes the application cannot invoked web service method. The error which I get is :

16:58:52,332  INFO HTTPSender:202 - Unable to sendViaPost to url[http://prodbus.farm.globul.bg:8000/BPACommunicationWS/BPACommunicationWS]
org.apache.axis2.AxisFault: Transport error: 401 Error: Authorization Required
                    at org.apache.axis2.transport.http.HTTPSender.handleResponse(HTTPSender.java:310)
                    at org.apache.axis2.transport.http.HTTPSender.sendViaPost(HTTPSender.java:200)
                    at org.apache.axis2.transport.http.HTTPSender.send(HTTPSender.java:76)
                    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.writeMessageWithCommons(CommonsHTTPTransportSender.java:400)
                    at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:225)
                    at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:435)
                    at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:402)
                    at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:229)
                    at org.apache.axis2.client.OperationClient.execute(OperationClient.java:165)

The problem is fixed after restart the OC4J instance. Also the allocation of the memory is growing a lot.

Does somebody know the reason of this? I used axis version 1.5.1.

Thanks in advance.

The problem was that I use axis2 for a web service with authorization in ClassOne and in ClassTwo I use axis2 without authoiztion and somehow when I make the authorization in ClassOne axis2 remember that there is a authorization and do it in ClassTwo. I remove also the set preemptive flag and everything works fine.