If config_inc.php has the following lines while upgrading from 1.2.x:

$g_show_detailed_errors = ON;

$g_display_errors = array(
E_USER_ERROR => DISPLAY_ERROR_HALT,
E_WARNING => DISPLAY_ERROR_HALT,
E_ALL => DISPLAY_ERROR_HALT,
E_USER_ERROR => DISPLAY_ERROR_HALT,
);

function install_check_token_serialization() {
$query = 'SELECT * FROM {tokens} WHERE type=1 or type=2 or type=5';

$t_result = db_query( $query );
while( $t_row = db_fetch_array( $t_result ) ) {
    $t_id = $t_row['id'];
    $t_value = $t_row['value'];

**** $t_token = unserialize( $t_value );