Trying to authenticate against Active Directory I get:

Root cause of LDAP connect error undefined method `to_ber’ for #<yaml::privatetype:0x2b3e8c1c>:
/home/jake/Applications/mingle/vendor/gems/ruby-net-ldap-0.0.4/lib/net/ldap.rb:1100:in `bind’
/home/jake/Applications/mingle/vendor/gems/ruby-net-ldap-0.0.4/lib/net/ldap.rb:701:in `bind’
/home/jake/Applications/mingle/vendor/plugins/ldap_auth/lib/ldap_auth.rb:21:in `authenticate?’
/home/jake/Applications/mingle/lib/authenticator.rb:7:in `authenticate?’
/home/jake/Applications/mingle/vendor/plugins/ldap_auth/../../../lib/login_system.rb:19:in `authenticate’
/home/jake/Applications/mingle/app/controllers/profile_controller.rb:22:in `login’

I know this server and these settings are correct since I use them for other things such as SVN.

can you post your auth-config.yml ? ( remember to remove the password when you post the configuration and/or change the DN if you are not comfortable to post it here. )