The problem is your update function. $old_instance is kind of special variable. The simplest is
function update($new_instance, $old_instance) {
return $new_instance;
}
For the safe
function update($new_instance, $old_instance) {
$instance = array();
$instance['name'] = htmlentities($new_instance['name']);
$instance['divclass'] = htmlentities($new_instance['divclass']);
$instance['paypal'] = htmlentities($new_instance['paypal']);
return $instance;
}