Never Appears In Page Node

Problem

This is most certainly user-error but I've been looking it at it a few hours, search the closed issued reports and documentation, and still can not seem to fix it. Thank you, in advance, for your help and patience with this drupal newbie. :-)

Using the very good documentation for this module I was able to get the module installed. I was able to create a block using the module which points to a folder in which I have some image files. I have added that block to a content region.

I tried explicitly creating a page which uses the PHP Filter input mode which contains the following PHP:

<?php
$block = module_invoke('ddblock', 'block', 'view', 4);
if (null !== $block) {
    var_dump($block);
}
else {
    print("\$block was null\n");
}
?>

I have tried it with the 4 in quotes and not (in case something was checking types). The page always has the page title followed by '$block was null'. The URL for the block is '/admin/build/block/configure/ddblock/4'. I was expecting the gallery to appear on the page.

Additional Troubleshooting

As an additional test I configured the block to 'Show only on the listed pages'; and I list "admin/*" (without quotes) then the gallery displays successfully on my admin pages. Good - I know the gallery works. However, if I then configure the block to only 'Show on every page except the listed pages' with the same filter (admin/*) the gallery does not appear to show up anywhere. I would have expected this gallery to show up on all pages except the admin pages... no joy.

So it seems there is some other step I am missing. I can see that the gallery can work (previous paragraph) but I can not get it to appear in a page node.

Additional Details

In case it matters I am running drupal-6.15 on PHP version 5.3.0 (WAMP server)
I am also using jquery_update-6.x-1.1.

I also have HTML-Purifier CKEditor and ICME related modules installed.
However, based on closed tickets I reviewed I verified that they are not inserting any HTML into my page.
I can save the page, and then reedit it without anything having changed.

Thanks again for your help!