Menu doesnt appear on custom 'not found' page On my site I have configured things so that the home page will appear if the URL doesnt exist.
(ie in admin/settings/error-reporting I set a replacement page for the 404 page.)

The problem is that the menu doesnt appear, so if a user lands here he cant use the site properly.

My menu is the 'primary menu' and has been placed in the left sidebar. I dont have any special setting for this block - eg no page 'includes' or 'excludes'. 

To help me debug can anyone tell me if this is the expected behaviour or any suggestions for what might have gone wrong?

I'm using Drupal 6.
Drupal doesn't render the region of your theme that your primary menu is in; there's a module to change this behavior:


  On 404 Not Found error pages, Drupal will skip rendering of several
  pieces of your website for performance reasons. Some of these include:
  
  
  The "Left" and "Right" regions of your theme.  
  The "Primary links" block and any other menu links block.*  
  The Primary links and Secondary links of your theme.*
  
  
  *Unless you have configured a "Default 404 (not found) page" on
  admin/settings/error-reporting.


From 404 Blocks module description.