maybe the problem was in ".htaccess" file... it's stored in root folder.
I use this file to stablish a rule to disable any access to different files or folders (for security)
look at this code (the lines with # are also comments):
#added to access custom files - sub domains or special folders
#--------
#subdomains and add on domains
#RewriteCond %{HTTP_HOST} !sub_addondomain.com$
#RewriteCond %{HTTP_HOST} !myaddondomain.com$
#
# folders
#RewriteCond %{REQUEST_URI} !/creservas/
RewriteCond %{REQUEST_URI} !/phplist/
#
# files
#RewriteCond %{REQUEST_URI} !/filejs.js
RewriteCond %{REQUEST_URI} !/phplist/index.php
RewriteCond %{REQUEST_URI} !^/index\.php
RewriteCond %{REQUEST_URI} !/ow_updates/index\.php
RewriteCond %{REQUEST_URI} !/ow_updates/
RewriteCond %{REQUEST_URI} !/ow_cron/run\.php
RewriteCond %{REQUEST_URI} (/|\.php|\.html|\.htm|\.xml|\.feed|robots\.txt|\.raw|/[^.]*)$ [NC]
RewriteRule (.*) index.php
all files or folders not specified in the rules, can't load because de server redirect to index
... but perhaps your problem is other because normally, with this rules, you don't see any error.