Sorry, Adam, I thought I had responded to this.
I upgraded from 6.3 to 6.4 to see if that fixed it, but it didn't. The errors occur in IE 6 and 7 when clicking "Save" or the red x to close the Make Template dialog when creating a new template. Once the errors occur, none of the menu buttons work in the main editor until the entire page is refreshed.
I'm editing the HTML files that are created in the "Make Template" dialog. The errors only occur when exiting from a newly created template. They do not occur when closing the dialog after editing an existing template.
Thanks,
Bruce