--- scheduler.module.old	2011-11-29 13:07:46.297126000 -0700
+++ scheduler.module	2011-11-29 14:24:13.380627113 -0700
@@ -386,7 +386,7 @@ function scheduler_list() {
  * FALSE, if $str is malformed
  */
 function _scheduler_strtotime($str) {
-  if ($str && trim($str) != "" ) {
+  if (is_string($str) && $str && trim($str) != "") {
     $date_format = variable_get('scheduler_date_format', SCHEDULER_DATE_FORMAT);
 
     if (_scheduler_use_date_popup()) {