SOAP UI 4.0.1 PRO ERROR

hi friends...
when i am trying to load the http://localhost:8080/jbilling/services/api?wsdl in SOAP UI it given error asError loading [http://localhost:8080/jbilling/services/api?wsdl]: org.apache.xmlbeans.XmlException: org.apache.xmlbeans.XmlException: error: Reference to undefined entity: nbs.... The same URL(http://localhost:8080/jbilling/services/api?wsdl) in the browser working fine and also it returned XML file.. BUT the URL not working in SOAP UI it giving above error ...

Thanks in advance for helping...