OpenSAML user discussion

I had the following code

SAMLIdentifier idgen = SAMLIdentifierFactory.getInstance();

a.setId(idgen.getIdentifier());
and the exception is here
a.sign(XMLSignature.ALGO_ID_SIGNATURE_RSA_SHA1, 
MessageDigestAlgorithm.ALGO_ID_DIGEST_SHA1,keyPair.getPrivate(), null);


[6/26/08 12:32:55:938 CDT] 00000026 SystemOut     O 
org.apache.xml.security.signature.XMLSignatureException: Cannot resolve 
element with ID _5d2266975a84085eea3e6f708eaad917
Original Exception was 
org.apache.xml.security.signature.ReferenceNotInitializedException: Cannot 
resolve element with ID _5d2266975a84085eea3e6f708eaad917
Original Exception was 
org.apache.xml.security.signature.ReferenceNotInitializedException: Cannot 
resolve element with ID _5d2266975a84085eea3e6f708eaad917
Original Exception was 
org.apache.xml.security.signature.ReferenceNotInitializedException: Cannot 
resolve element with ID _5d2266975a84085eea3e6f708eaad917
Original Exception was 
org.apache.xml.security.utils.resolver.ResourceResolverException: Cannot 
resolve element with ID _5d2266975a84085eea3e6f708eaad917
        at org.opensaml.SAMLSignedObject.sign(Unknown Source