Authentication plugin 'dialog' cannot be loaded

Hello all,

I am using HeidiSQL 9.1 on Win 8.1 to connect to a MariaDB 5.5 instance on CentOS 6.6. I have configured the auth_pam.so plugin and I can authenticate as a Windows Active Directory user if I access the MariaDB from another Linux instance via command line. Any attempt to connect to the same MariaDB instance from Windows (using HeidiSQL or MySQL Workbench) is met with the error in the subject line.

I have confirmed that the dialog.dll is located at C:\Program Files\HeidiSQL\plugins

I think this might be a Windows error - but was hoping someone here might point me in the right direction to start debugging. I have read that HeidiSQL was the only client capable of pam authentication out of the box so I was disappointed to find it not working.

Any advice?

Thanks!