--- loncom/interface/loncommon.pm	2010/11/09 21:18:16	1.948.2.12
+++ loncom/interface/loncommon.pm	2010/11/17 20:41:53	1.948.2.13
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.948.2.12 2010/11/09 21:18:16 raeburn Exp $
+# $Id: loncommon.pm,v 1.948.2.13 2010/11/17 20:41:53 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -2284,12 +2284,16 @@ function changed_text(choice,currentform
 }
 
 function set_auth_radio_buttons(newvalue,currentform) {
+    var numauthchoices = currentform.login.length;
+    if (typeof numauthchoices  == "undefined") {
+        return;
+    }
     var i=0;
-    while (i < currentform.login.length) {
+    while (i < numauthchoices) {) {
         if (currentform.login[i].value == newvalue) { break; }
         i++;
     }
-    if (i == currentform.login.length) {
+    if (i == numauthchoices) {
         return;
     }
     current.radiovalue = newvalue;