Various strange behaviors with multiple editors on page and Firebug

Issue Summary

I've been having issues where the content of an editor (in the 'body' field of a CCK-enhanced content type) gets messed up in various ways: it becomes duplicated multiple times, and/or the drupal break moves or is duplicated, often accompanied by the javascript error:

I had two editors on the page, and I'm using Firefox 3 with Firebug. The editors seemed to work in Safari, and (inexplicably) worked when Firebug was disabled. The behavior was inconsistent, so it was hard to nail down, but it almost always caused some error.
It seems that removing the 2nd editor - so there is only one per page - fixes the problems, Firebug on or off. I tested this a few times and it seems to hold up. So my conclusion is that having multiple editors on the page causes the javascript bug which causes the strange (but inconsistent) behaviors with the text.