You've hit a pretty old (about a year) forum thread, but ...
mdl_config is a table in the database for your Moodle. To see values contained in the database one must use some app that can see the database tables, etc. One such: phpmyadmin. Or, if one is lucky enough to have terminal access to the server there is command line:
mysql -u root -p[password];
select * from `mdl_config` where `name` like "%blockedip%";
One will be able override entries for blockedip via the config.php file:
$CFG->blockedip = '';
Setting is in affect for as long as the line exist.
This won't work if one is working with a Windows/Mac package meant for development ... those are set to use localhost only and making them accessible involves more than just the blockedip setting. That, BTW, is not recommended.
'spirit of sharing', Ken