Thanks for the admin access. The white page happens whenever there is a PHP Fatal error on your site. That comes from invalid PHP code. Normally, setting the Error Reporting setting in the Joomla -> Global Configuration area to 'Maximum' will display the actual error. On your site, either the host or an extension has disabled the output of errors. In that case, you'll need to contact the host to get the PHP error logs (not Apache Error Logs) to determine the cause.
The problem is *not* from the modifications you made to the SCLogin module. Even with that module disabled, the white page still occurs. When a module is disabled, it's code does not execute, so even if there were an error in that file, it wouldn't cause the white error you see.
You'll need to determine what is actually causing the PHP error and fix that problem. To double-check the problem isn't in JFBConnect, you can always re-install our extension. That will revert any changes you've made and may get you going again. From what I can see though, by disabling both the JFBCSystem plugin and the SCLogin module, the error is not from our extension or modifications you made to it.
I hope that helps get you started. Once you have the error resolved, or at least have the actual error message from the PHP error logs, we'll gladly help diagnose things further however we can.
Thanks,
Alex