LDAP authentication against Active Directory seems to be broken in 3.4 Enterprise

LDAP authentication against Active Directory seems to be broken in 3.4 Enterprise.
The following errors are logged after activating extended logs in log4j.properties:

2005-11-10 17:55:51,872 DEBUG [user.provider.ldap.LDAPCredentialsProvider] Doing initial search: username='cn=advestigo,OU=SBSUsers,OU=Users,OU=MyBusiness,DC=advestigo,DC=loc', base='OU=SBSUsers,OU=Users,OU=MyBusiness,DC=advestigo,DC=loc', filter='sAMAccountName=xxx'
2005-11-10 17:55:51,872 ERROR [user.provider.ldap.LDAPCredentialsProvider] Connected to LDAP, but could not perform authenticated search from base 'OU=SBSUsers,OU=Users,OU=MyBusiness,DC=advestigo,DC=loc'
2005-11-10 17:55:51,872 DEBUG [user.provider.ldap.LDAPCredentialsProvider] Couldn't authenticate against LDAP, trying other CredentialsProviders

I'm using the exact same osuser.xml file as in our production 3.3 server, which is working fine (on the same machine)