404 errors on pages that exist – index location error

I have a site running that when I go to the URL it gives me the “index of /” listing. If I add a space between the domain name and the index.php I can get to the site. Not sure what is causing this. If I get to the site all the links (menu to pages) a 404 – not found error (I see them in the admin). I have tried resetting the premalinks and that has not resolved the issue. Any help would be great as my backup is from the same stated condition.