lookupUserFromDN to Active Directory fails after 405 upgrade

Both in the administration and in the user rights panels for containers, 
looking up users in Active Directory yields the following errors.

Lookup of Active Directory groups works and login to the site with an Active 
Directory user is no problem. The new settings in group-router-config.xml 
and router-config.xml appear to be configured correctly, including the 
<factory>com.sun.jndi.ldap.LdapCtxFactory</factory> setting to which the 
problem seems related.

usermanager.JahiaUserManagerLDAPProvider lookupUserFromDN - JNDI warning
javax.naming.PartialResultException. Root exception is
javax.naming.AuthenticationException: [LDAP: error code 49 - 80090308: 
LdapErr: DSID-0C09030B, comment: AcceptSecurityContext error, data 52e, v893
<snip>
WARN usermanager.JahiaUserManagerLDAPProvider lookupUserFromDN - JNDI 
warning
javax.naming.NoInitialContextException: Need to specify class name in 
environment or system property, or as an applet parameter, or in an 
application resource file: java.naming.factory.initial
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:652)

Any help is appreciated
pascal