Problem with auth_ldap in Apache 2.0.47 vs Active Directory

Hi -

Can anyone help with a problem I'm experiencing with auth_ldap?

I have built Apache 2.0.47 with the auth_ldap module (on Solaris and
want to use it to authenticate against our Active Directory database.

I have got to a point where it is clearly connecting to AD but the
response seems to be perhaps a bit odd.

If I provide an INCORRECT username and password, Apache logs

[warn] [client xxx.xxx.xxx.xxx] [26593] auth_ldap authenticate: user
fred authentication failed; URI /testauth [ldap_simple_bind_s() to check
user credentials failed][Invalid credentials]

Well and good, but if I supply a CORRECT username and password,
authentication still fails but Apache now logs

[warn] [client xxx.xxx.xxx.xxx] [26593] auth_ldap authenticate: user
fred authentication failed; URI /testauth [User not found][No such object]

....so it seems that the username and password are checked, but if they
are correct a different error is still generated from somewhere.

The directory I'm testing against is configured as follows

<Directory /usr/local/apache2/htdocs/testauth>
AuthLDAPURL "ldap://our.machine/cn=users,dc=staff,dc=our-uni,dc=ac,dc=uk"
AuthLDAPBindDN "cn=ldapacct,cn=users,dc=staff,dc=our-uni,dc=ac,dc=uk"
AuthLDAPBindPassword abcdefgh
AuthType Basic
AuthName testauthldap
Require valid-user
</Directory>

Any ideas?

Thanks

Richard