soapUI help

hello everyone....newbie....and need help....we are pulling our hair out trying to figure out what we are doing wrong. we are trying to test a webservice between us and a client and we keep getting faultcode>soap:Server.75275</faultcode><faultstring>The verify component could not verify the digital signature for the given signer.</faultstring>. Client says "The public key is no issue. The signing you are doing with the pvt key at ur end and how it comes thru to us".

Your help is greatly appreciated.