I have 3 servers, a localhost apache server, a testing remote server and the production live server.
I have the same installation of codeigniter and site set-up on a
Maybe something is wrong with your .htaccess file?
Once I had problem when I moved application to production server, because RewriteBase was set to some directory on development server.
On my production server application was in web root directory, so RewriteBase should be /, and i had /something there.
Once i had silly problem with upper/lowercases, when i moved site from development server (windows) to production (linux).