An AJAX HTTP error occurred. HTTP Result Code: 200

This is my first time to install Drupal, and it is installed online (rather than local). After "Set up database" and before "Install profile" during installation, I got the following message:

An AJAX HTTP error occurred. HTTP Result Code: 200 Debugging information follows. Path: http://circle.serw5.com/install.php?profile=standard&locale=en&id=1&op=do StatusText: OK ResponseText: {"status":true,"percentage":"18","message":"Completed 5 of 28.\u003cbr \/\u003eInstalled \u003cem\u003eField\u003c\/em\u003e module."} Free Hosting Free Hosting Web Hosting VPS Hosting

Above the message, there was a link "continue with the error page". After clicking the link, I was asked to do other configurations, and it shows that other steps ("Install profile" and "Configure site") are finished. Although I can input content immediately, if I log out and visit the web site again, I would be denied access. I only got the following message:

Access denied
You are not authorized to access this page.

So any people who didn't register could not visit the site, nor could they register.

So what should I do? Could anybody give me some help? Thank you so much!