I'm not able to reproduce this.
Are you using Code View when inserting the HTML Editor?
You should be using Design View instead.
it sounds to me like you have an existing text area that you are converting to an HTML Editor instance?
In Design View, select the Text area, then in the Code inspector along the bottom of the design Window, select the Text area tag, then go to WebAssist -> Forms -> HTML Editor -> Insert Editor to insert the new HTML Editor instance.