Message part not recognized.

Hello,

I'm getting the a SOAP fault informing me that the message is note
recognized. Specifically,
Message part (http::/www.company.com/sps/artifactWithDefaultSpEntityRequest
was not recognized, (Does is exist in WSDL?) The WSDL does contain
message definition and was validated with the wsdlvalidator utility.
Any idea why am I getting this fault? The relevant WSDL excerpts
follow.

<xsd:schema>
<wsdl:types>
...
<xsd:element name="artifactWithDefaultSpEntityRequest"
type="tns:ArtifactWithDefaultSpEntityType">
</xsd:element>

<xsd:complexType name="ArtifactWithDefaultSpEntityType">
<xsd:sequence>
<xsd:element name="nameId" type="xsd:string"
maxOccurs="1" minOccurs="1">
</xsd:element>
<xsd:element name="targetUrl" type="xsd:string"
maxOccurs="1" minOccurs="1">
</xsd:element>
<xsd:element name="attributes"
type="tns:AttributeType" maxOccurs="unbounded"
minOccurs="0"></xsd:element>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="artifactWithDefaultSpEntityFault"
type="tns:SpsFaultType">

</xsd:element>
</xsd:schema>
</wsdl:types>
...
<wsdl:message name="artifactWithDefaultSpEntityRequest">
<wsdl:part name="parameters"
element="tns:artifactWithDefaultSpEntityRequest">
</wsdl:part>
</wsdl:message>
...
<wsdl:portType name="svc">
<wsdl:operation name="artifactWithDefaultSpEntity">
<wsdl:input
message="tns:artifactWithDefaultSpEntityRequest"></wsdl:input>
<wsdl:output
message="tns:artifactWithDefaultSpEntityResponse"></wsdl:output>
<wsdl:fault name="fault"
message="tns:artifactWithDefaultSpEntityFault"></wsdl:fault>
</wsdl:operation>
</wsdl:portType>
<wsdl:binding name="svcSOAP" type="tns:svc">
<wsdl:operation name="artifactWithDefaultSpEntity">
<soap:operation
soapAction="http://www.company.com/sps/artifactWithDefaultSpEntity"/>
<wsdl:input>
<soap:body use="literal"/>
</wsdl:input>
<wsdl:output>
<soap:body use="literal"/>
</wsdl:output>
......
</wsdl:binding>