CodeIgniter with php5 - CI-generated 404 Error

[eluser]Eric Cope[/eluser]
Hello all,
I am developing an admin page for a client using CodeIgniter. I started developing in php4. However, now the server supports php5 only under the following conditions:

1. all php files have extension .php5
2. .htaccess be edited to include "AddType application/x-httpd-php5 .php5 .php"

I chose the second option. Now, I get a codeIgniter-generated 404 error for root page.
Any ideas?

If I remove that line in my .htaccess page, it functions properly again.