pmenard, thank you for your time. I appreciate your feedback but I still am convinced that there is an issue with media tags. This plugin is the only plugin I have installed, and when I deactivate the plugin the attach dialog box works correctly. I have also tried changing themes to see if that was the cause.
When I do a large-scope search for a term like “e”, I get a list of posts for either a post search or page search. In other words, clicking the Page radio button has the same effect as clicking the Post radio button.
Hope this helps.