I installed WordPress in a directory called 'WordPress'. Note the capital W and capital P. I could not get my website to start after typing 'www.mywebsite.org/wordpress'.
Finally, I tried 'www.mywebsite.org/WordPress', and it worked!
This same gotcha had me stumped for a while when I had to edit the index.php after changing the site URL to just 'www.mywebsite.org' I had followed the instructions from WordPress, which used '/wordpress' in the example.
I've not seen any mention of case-sensitivity in the documentation I have followed so far.