diff -Naur drupal-4.7.2.old/modules/filter.module drupal-4.7.2/modules/filter.module
--- drupal-4.7.2.old/modules/filter.module	2006-05-04 07:13:00.000000000 -0400
+++ drupal-4.7.2/modules/filter.module	2006-06-19 10:25:54.200011775 -0400
@@ -794,9 +794,19 @@
  *   HTML for the form element.
  */
 function filter_form($value = FILTER_FORMAT_DEFAULT, $weight = NULL, $parents = array('format')) {
-  $value = filter_resolve_format($value);
+
   $formats = filter_formats();
 
+  // Pick a default if we have none
+  if ($value != FILTER_FORMAT_DEFAULT) {
+    $value = filter_resolve_format($value);
+  }
+  else {
+    $default_format = end($formats);
+    reset($formats);
+    $value = $default_format->format;
+  }
+
   $extra = l(t('More information about formatting options'), 'filter/tips');
 
   if (count($formats) > 1) {