diff -r 51386f1852b8 -r f26a69c40431 includes/clientside/tinymce/plugins/media/js/media.js
--- a/includes/clientside/tinymce/plugins/media/js/media.js	Thu Mar 06 20:45:46 2008 -0500
+++ b/includes/clientside/tinymce/plugins/media/js/media.js	Thu Mar 06 20:47:11 2008 -0500
@@ -493,6 +493,9 @@
 	var e = document.forms[0].elements[(p != null ? p + "_" : "") + n];
 	var v = e.type == "text" ? e.value : e.options[e.selectedIndex].value;
 
+	if (n == 'src')
+		v = tinyMCEPopup.editor.convertURL(v, 'src', null);
+
 	return ((n == d || v == '') ? '' : n + ":'" + jsEncode(v) + "',");
 }