Same problem here, the wsdl does not conform to the standard that SAP accepts. According to the error message generated by SAP you can only have one part in the wsdl and this wsdl has many.
Either you change the wsdl yourself before you use it to generate a proxy (not recommended) or you ask the service provider for another wsdl with only one part.
Test the wsdl and check the requirements set by SAP for the wsdl format in this link.
http://wiki.scn.sap.com/wiki/display/TechTSG/Generation+of+Consumer+Proxy+fails