Depending on specific server security settings, it is possible to receive a message such as:

Error Saving Database Administrator credentials to the web.config file.: An error occurred loading a configuration file: Access to the path 'C:\inetpub\wwwroot\MFS\15omdzsa.tmp' is denied (C:\inetpub\wwwroot\MFS\web.config)

If this occurs, please add "Full Control" permissions to the Mi-Forms Server installation folder (in the example above c:\inetpub\wwwroot\mfs) to the administrative user that is being specified while attempting to save.