Add Menu Block (module) Menu To Page tpl
It seems like you're mixing the Drupal 6 and Drupal 7 api a little bit.

If you're on Drupal 7, you should print out your block like this:

&lt;?php
$block = module_invoke('module_name', 'block_view', 'block_delta');
print render($block['content']);
?&gt;


Note the 'print render'. (You're missing the 'render' part if you're on Drupal 7. 

The only things you need to change are to put 'menu_block' for the 'module_name' and your block's machine name for 'block_delta'.

More info and examples are on drupal.org: http://drupal.org/node/26502 

Does that work for you?

============ Edit ==============

On the other hand, if you're on Drupal 6, your call should look something like this:

&lt;?php
$block = module_invoke('module_name', 'block', 'view', 'block_delta');
print $block['content'];
?&gt;


In this case, you're fine with the just 'print $block['content']', but your arguments are a little off.  From what you're saying though, it sounds like you're on Drupal 7, and are just returning the array without rendering it!!! :-)