Controller "users"

[eluser]Unknown[/eluser]
I was trying to write controller called "users".
URL like "domain.com/users" works as expected.
URL like "domain.com/users/add" is showing 404 error.
URL like "domain.com/index.php/users/add" works as expected.
When I renamed controller to "user", all links work fine and other controllers were working fine all the time.

What was wrong with this thing?

[eluser]Eric Barnes[/eluser]
Sounds to me like a .htaccess issue unless you have some form of custom routes over riding it.