Thanks, a few other errors popped up so I noticed that the authentication.php file was different than those of other sites that have no issue for some reason. I changed the file with a working one and no problem now.
Thanks for your help.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.