Actually, I think the problem is you re-named
block-menu.tpl.php instead of copying it as it works for me here. If it doesn't for you, or you want to theme a specific menu block, you can do something like this:
Copy the default
block.tpl.php to your theme's directory if it's not already there.
Examine your html source and look for the ID of any block, eg
<div id="block-menu-my-menu" ....> and then,
- Create a new
block-menu-my-menu.tpl.php in your theme's directory, eg, block-BLOCK_ID.tpl.php.
You need to have BOTH otherwise Drupal 6 won't look for the specific block template override.
In either case, you have to clear the cache after creating both templates.
Now you should be able to theme this specific menu block.
For good measure, if you want to keep things clean, you can also create a directory structure for all of the templates, eg, create a tpl directory and then in there have subdirectories like
block, node, page, etc, and put all your various templates in there.
To be more precise, read: Drupal 6 Template Suggestions
What's a template suggestion? It's an alternate template
(.tpl.php) file that you have created to override the base or
original template file. Suggestions only work when they are placed in
the same directory as the base templates. In other words, if you
comment-blog.tpl.php to display in your browser,
comment.tpl.php also needs to exist inside your theme's folder and the two files must be in the same directory.
I am not sure what kind of development environment you have, but hopefully it is similar to MAMP, which I use for quick stuff on my MacBook:
- cd /applications/mamp/htdocs/modules/system
- cp block.tpl.php /applications/mamp/htdocs/sites/all/themes/YOURTHEME
- cd /applications/mamp/htdocs/sites/all/themes/YOURTHEME
- cp block.tpl.php block-menu.tpl.php
Now, if YOURTHEME already has a
block.tpl.php, you can omit step 2, but just make sure that when all is said and done somewhere in or under the YOURTHERE directory, there is a directory that contains both
block-menu.tpl.php. It could be in the base level directory, it could be in a subdirectory, regardless, just make sure both files are there. Also, make sure that YOURTHEME doesn't have a
block.tpl.php elsewhere. If it does, make sure that
block-menu.tpl.php is in that directory, eg, that you don't have two sets of
block-menu.tpl.php files in different directories in YOURTHEME's directory structure for that would be confusing the theme registry build process and it would pick up only one of them.
Clear all caches to make sure the theme registry is rebuilt to see these new templates. If you have the Admin Menu module installed you can do this easily from the leftmost dropdown menu.
Now you can edit
block-menu.tpl.php to theme all blocks created by the menu module.