Apache 2.0.48: mod_auth_ldap and Active Directory

Yo.

I'm running Apache/2.0.48 (Win32) with mod_ssl/2.0.48 and
OpenSSL/0.9.7c on a Windows 2000 Advanced Server SP4. I've configured
the mod_auth_ldap that came with the Apache distribution to validate
user accounts against my ADS.

Therefore I've included the following lines into my httpd.conf:

LoadModule auth_ldap_module modules/mod_auth_ldap.so
LoadModule ldap_module modules/util_ldap.so

and

<Directory "C:/Program Files/Apache Group/Apache2/htdocs">
Options Indexes FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
AuthName "Global Information Systems Domain"
AuthType Basic
AuthLDAPUrl "ldap://localhost/dc=globis,dc=infk,dc=d,dc=ethz,dc=ch?sAMAccountNam e?sub?(objectCategory=Person)(objectClass=User)"
AuthLDAPBindDN "cn=LDAPUser,cn=Users,dc=globis,dc=infk,dc=d,dc=et hz,dc=ch"
AuthLDAPBindPassword "*********"
require valid-user
</Directory>

Now, the problem is REALLY strange! As long as the users enter their
credentials correctly, everything works perfectly... But (and it's a
big BUT) as soon someone enters a wrong user/password, the validation
always fails from any machine and browser until the Apache service is
restarted...

The following warning is logged in the "error_log" file once:
[Thu Feb 26 21:37:13 2004] [warn] [client 129.132.13.8] [6884]
auth_ldap authenticate: user abc authentication failed; URI /
[ldap_simple_bind_s() to check user credentials failed][Invalid
Credentials]

Every subsequent attempt to log in produces the following error:
[Thu Feb 26 21:37:37 2004] [warn] [client 129.132.13.8] [6884]
auth_ldap authenticate: user abc authentication failed; URI / [User
not found][No Such Object]
[Thu Feb 26 21:38:39 2004] [warn] [client 129.132.13.28] [6884]
auth_ldap authenticate: user xyz authentication failed; URI / [User
not found][No Such Object]

Any help, suggestions or ideas are greatly appreciated!

MfG,
Michael.