Dispose a RadEditor with AJAX (ASP UpdatePanel, RadAjaxpanel, RadAjaxManager) and if you attempt to show a floating toolbar (i.e. all ToolbarMode options except Default and RibbonBar) a JS error is thrown.
There are two workarounds:
1) use ASP UpdatePanel with ChildrenAsTriggers=false and updateMode=Conditional
2) override several RadWindow methods to prevent the error (these scripts must be placed just before the closing </form> tag):
	<script type="text/javascript">
		Telerik.Web.UI.RadWindow.prototype._moveElementToShowOutOfView = function ()
		{
			if (this.view)
				this.view.moveOutOfSight();
		}

		Telerik.Web.UI.RadWindow.prototype.setVisible = function (toShow)
		{
			if (this.view)
			{
				if (toShow)
					this.view.show();
				else
					this.view.hide();
			}
		}
	</script>