diff -r 5882f0eebb34 -r e3b94bd055dc includes/clientside/tinymce/plugins/advimage/js/image.js
--- a/includes/clientside/tinymce/plugins/advimage/js/image.js	Mon Dec 21 15:41:05 2009 -0500
+++ b/includes/clientside/tinymce/plugins/advimage/js/image.js	Tue Dec 22 13:09:59 2009 -0500
@@ -272,6 +272,7 @@
 			cl = tinyMCEPopup.editor.dom.getClasses();
 
 		if (cl.length > 0) {
+			lst.options.length = 0;
 			lst.options[lst.options.length] = new Option(tinyMCEPopup.getLang('not_set'), '');
 
 			tinymce.each(cl, function(o) {
@@ -285,6 +286,7 @@
 		var dom = tinyMCEPopup.dom, lst = dom.get(id), v, cl;
 
 		l = window[l];
+		lst.options.length = 0;
 
 		if (l && l.length > 0) {
 			lst.options[lst.options.length] = new Option('', '');