$route['404_override'] bug problem

[eluser]bottleboot[/eluser]
Hi.

I've been having issues getting the $route['404_override'] to work.
The solutions posted on this forum and elsewhere don't seem to work for me or are unclear.

How do I tackle this?

Code:

$route['404_override'] = 'controller/method';

This does not work.

Solutions with MY_Controller, MY_Exceptions etc neither.
Threads and topic around this issue date back from months ago.

I don't get it.
Help!