.htaccess question: 404 Results from Different Paths on Server vs. Localhost?

The problem is because of  you dont have file .htaccess in xyz or you have but It only works on root directory, please read document guide or search google for creating .htaccess for Codeigniter,
then you will find some articles about creating, configuration for that file, place It in /xyz/ folder, then You have to modify your .htaccess file to run CI from any directory (include subdirectories)
FROM:

Code:

RewriteRule ^(.*)$ /index.php/$1

TO:

Code:

RewriteRule ^(.*)$ ./index.php/$1

If you follow my instruction then I think you will be ok.
Another way is add index.php in your url
http://myDomainName/xyz/index.php
http://myDomainName/xyz/index.php/controller_name/
http://myDomainName/xyz/index.php/controller_name/action_name
http://myDomainName/xyz/index.php/controller_name/action_name/parameters_etc
P/S: make sure mod rewrite (htaccess) has been turned on your server.