Open inc/config.php
Find line 9 ($scriptpath = ''; //The folder you installed this script in)
Make sure it looks like that, and not public_html between the ' and '
But if you happen to break the script after uploading this, then you need to remove files from this extra public_html folder, there is only one REAL one with meaning on any server, you're using a secondary one, so it seems.
I'd recommend, if you have no members just reinstall the script and when it asks for the script path in the install, leave it blank (if the script is in the MAIN one)
See this:
http://gyazo.com/2b75e9a6d126c4d175ce8182a0941d23
For an example of where the MAIN one is located when you log into your FTP server