Codeigniter and WordPress redirect to install.php

I’m building a website which requires both Codeigniter and WordPress to work side-by-side. So far I’ve gotten them to play nicely together, but I finally ran into a brick wall.

Codeigniter runs the website, except for the WordPress blog which runs from a subfolder, for example: http://mysite.com/wordpress/.

To display a page using Codeigniter, I need to call WordPress functions such as get_header, get_sidebar, and get_footer. In order for these to work, I need to include wp-blog-header.php. However, as soon as wp-blog-header.php is called, the browser redirects me to the wp-admin/install.php page (which does not exist anymore).

I don’t believe this is a configuration problem, because the WordPress blog pages run fine by themselves. I did a repair on the entire database with no change. I’m thinking that WordPress is noticing that the request URL does not belong to itself, so it sends a redirect header to the browser, but I’m not sure.

Anyone have any ideas on why it’s redirecting? Thanks.