When editing an ODF content (with htmleditors hidden in tabs), many JS error popups are displayed one after the other (see screenshot).
It seems there is a problem with htmlarea.js when executing this block, introduced in version 2.9.20 :

if (!HTMLArea.is_ie)
{
	// disable firefox accelerators on tables
	editor.execCommand('enableInlineTableEditing', false, false);
}

Maybe creating the htmlarea in "no debug" mode will resolve the problem.