Maybe the DNS records you created for your domain are not configured correctly, or have not yet propagated. I’m basing that on this post: Bizarre installation problem re: specific domain name - #2 by david.
Try running the following from a terminal on your computer, with the domain name you are using for your site substituted for www.example.com
host www.example.com
If you can share the output here, someone may be able to spot an issue.