I have installed cck_map + TinyMCE on 5.10 Drupal (fairly clean and vanilla).

I have noticed the following behaviour in Firefox 3 when I have a text area and a cck_map item in the same node. If the "Show disable/enable rich text editor toggle:" toggle in the TinyMCE configuration screen is set to True the edit node page will not display properly in Firefox 3.

Workaround:
If you set the toggle to false then Firefox 3 will render the edit node page properly. You will have to enable the HTML button/plugin to allow pure HTML entry.