Index: pdo_moodle_database.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/dml/pdo_moodle_database.php,v
retrieving revision 1.8
diff -u -r1.8 pdo_moodle_database.php
--- pdo_moodle_database.php	13 Jul 2008 20:28:08 -0000	1.8
+++ pdo_moodle_database.php	24 Jul 2008 21:57:30 -0000
@@ -395,9 +395,14 @@
                 $value = (int)$value; // prevent "false" problems
             }
             if (!empty($column->enums)) {
-                if (!in_array((string)$value, $column->enums)) {
-                    debugging('Enum value '.s($value).' not allowed in field '.$field.' table '.$table.'.');
-                    return false;
+                // workaround for problem with wrong enums in mysql
+                if (is_null($value) and !$column->not_null) {
+                    // ok - nulls allowed
+                } else {
+                    if (!in_array((string)$value, $column->enums)) {
+                        debugging('Enum value '.s($value).' not allowed in field '.$field.' table '.$table.'.');
+                        return false;
+                    }
                 }
             }
             $cleaned[$field] = $value;