I have 4 HTML modules on a specific page. When trying to add one of those as an existing module to another page, they don't all show up. The settings are the same on all 4 of the modules. They are all just plain old basic HTML modules. Why would 1 of them not show up in the available modules? I can't be the only one running into this problem.

I've searched around for this with no luck, so please don't respond with "Have you looked at our forums?" or "Did you do a google search for this?"