Hi everyone. Thanks for the responses. I'm sorry if I started this topic in the wrong spot. I did not realize I was already in a subject when I hit the New Topic button.
Anyway, I have been testing this with various templates. I'm not sure which one is the Joomla default. However, when I switched to jp_default_1.5, I got the following result:

This is the first time I got any kind of an error message, and as you can see, there are no editor controls or buttons whatsoever. But as you can see, this seems to be a problem with this templates css (which I have experimented with in the past), and should not impact other templates.
To answer other questions, I do have a plugin installed that adds "image," "pagebreak," and "read more" links below the text box, but those are all currently disabled. I have uninstalled JCE, but I have JoomlaFCK, TinyMCE 2.0, and No Editor enabled (by the way, how do you upgrade TinyMCE to a newer version?). I have tried various templates, but the one I use for my site is from siteground and is called sitegroung-j15-11. JoomlaJCK is the default editor in Global settings, and in my user settings.
Dave