Index: /FCKeditor/trunk/editor/_source/classes/fckpanel.js
===================================================================
--- /FCKeditor/trunk/editor/_source/classes/fckpanel.js	(revision 403)
+++ /FCKeditor/trunk/editor/_source/classes/fckpanel.js	(revision 404)
@@ -162,5 +162,8 @@
 		// to return the correct width. Remove the first step and it will not
 		// work when the editor is in RTL.
-		iMainWidth = this.MainNode.offsetWidth ;
+		//
+		// The "|| this.MainNode.firstChild.offsetWidth" part has been added
+		// for Opera compatibility (see #570).
+		iMainWidth = this.MainNode.offsetWidth || this.MainNode.firstChild.offsetWidth ;
 
 		var oPos = FCKTools.GetElementPosition(