In my servlet, login is working, but when I run a query I get the following:

AxisFault

 faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException

 faultSubcode:

 faultString: java.io.IOException: No serializer found for class com.sforce.soap.enterprise._SessionHeader in registry org.apache.axis.encoding.TypeMappingImpl@13c550f

Here is the query code:

    QueryResult qr = null;

                //call the query saving the results in qr
                try {
                        qr = binding.query("select Name, numberOfEmployees, Id, Industry from Account");
                } catch (Exception e) {
                        e.printStackTrace();
                        return;
                }

                //always a good idea
                if (qr != null) {
                        records = qr.getRecords();

                        //we can loop through the returned records
                        for (int i=0;i<records.length;i++) {
                                //Because we asked for accounts we will convert
                                //the SObject for each record into an Account object
                                Account account = (Account)records[i];

                                //Now we can access any of the fields we had in the query
                                //select clause directly from the account variable
                                System.out.print(new Integer(i+1).toString() + ". ");
                                System.out.print(account.getName() + " - ");
                                System.out.println(account.getId().getValue());
                        }
                        System.out.println("");
                }