no term listed when "comment" button is used in navigation

The core comment module sets the breadcrumb on the reply pages. Since these reply pages are forms (associated with nodes, but not nodes), Custom breadcrumbs 6.x-1.x can't alter the breadcrumb defined by the comment module. Same goes for taxonomy_breadcrumb.

There is a way to accomplish this. Custom breadcrumbs could implement hook_form_alter and check to see if it is a comment (in reply to a node). If it is, then cb could load the node and run custom_breadcrumbs_nodeapi() to set a custom breadcrumb according to the type of the node associated with the comment.

I will see if I can implement this as a feature request in custom_breadcrumbs 6.x-2.x-dev.

<?php
/**
 * Implementation of hook_form_alter().
 */
function custom_breadcrumbs_form_alter(&$form, $form_state, $form_id) {
  // Provide custom breadcrumbs for comment forms associated with nodes.
  if ($form_id == 'comment_form' && isset($form['nid']['#value'])) {
    $node = node_load($form['nid']['#value']);
    // Call custom_breadcrumbs_nodeapi to provide a custom_breadcrumb for this comment.
    custom_breadcrumbs_nodeapi($node, 'alter', array(), array(1));
  }
}
?>

This seems to work in 6.x-2.x-dev. I haven't tested it in 6.x-1.x, but I think it should work there also. If you would like to try it out, you can place this function in custom_breadcrumbs.module, or apply this patch (to 6.x-2.x-dev).

Committed to 6.x-2.x for further testing.