Nevermind. I figured out what issue was. My compiler was corrupting the .htaccess file, which was triggering the site-wide error message on load. You can see that it's working now here:
http://www.igeniusstore.com/this-test.html
or
http://www.igeniusstore.com/this-test
Here's the basic code that I used:
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^(.*)$ $1.html
Thanks for all of your help. Cheers!