[eluser]CroNiX[/eluser]
Code:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
Try this .htaccess, which says if the request isn't a real (f)ile and it isn't a real (d)irectory, process the request with CI (index.php), otherwise process request as normal file/directory.
If this doesn't work, use your current line similar to the last RewriteRule that does work, but replace the other lines.