Shibboleth Developers

Details of current config. Trying to configure Shib 2 IdP  along with custom 
SP.
SP in java using axis and xerces. IdP installed over weblogic 9.2
1) SP communicates with IdP . The secure mechanism is IP based. 
2) SP communicates with Idp over fixed IP thru ssl and basic auth over http.
3) SP and IdP are in different. User login happens over IdP using container 
manager authentication.
4) User can succesfully login to IdP. the container authenticates to LDAP.
5) Redirect happens to  Sp along with the SAML artifact.

Issues encountered.
6) Sp makes a call back to IdP . IdP throws "Inbound message issuer was not 
authenticated." The call back in fact do authenticate to the container using 
user/pass.

Any one with suggestions please.