IllegalDataException from active-directory authentication failure

valid user/invalid password causes the following:

org.jdom.IllegalDataException: The data "Operation failed; nested exception is javax.naming.AuthenticationException: [LDAP: error code 49 - 80090308: LdapErr: DSID-0C090334, comment: AcceptSecurityContext error, data 52e, vece^@]" is not legal for a JDOM character content: 0x0 is not a legal XML character.
at org.jdom.Text.setText(Text.java:188)
at org.jdom.Text.<init>(Text.java:99)
at org.jdom.Element.addContent(Element.java:799)
at org.codehaus.xfire.util.stax.JDOMStreamWriter.writeCharacters(JDOMStreamWriter.java:208)

This causes SOAP to produce an empty response.