Hi, Hudson.
Have you changed actual LDAP server's port after you unchecked this SSL checkbox? What this checkbox does is just "tells" oxAuth (module of Gluu responsible for actual authentication of users) that all connections to specified "ldap_server:port" pair MUST be done using SSL. Or, in contrary, when unchecked, SSL MUST NOT be used when connecting.
So, if you didn't changed actual port (usually any LDAP server has at least 2 of them; for example, MS AD listens on 389 (no SSL) and 636 (LDAP over SSL); Gluu uses custom version of OpenDJ LDAP servers for storing its configuration and aggregating user personal info and by default it will be listening on ports 1389/1636 (noSSL/SSL)), then what happens is oxAuth now tries to connect to SSL enabled LDAP server's port without attempting to "build" SSL overlay first.
To roll-back to previous state you'll need to modify /opt/tomcat/conf/oxauth-ldap.properties and set "useSSL=" option back to "true", then restart the Gluu's service.
Regards,
Alex.