To resolve this issue go to:
yoursite.com/wp-content/plugins/mailchimp-widget/lib/ns_widget_mailchimp.class.php
onb line 249 there is:
$this->hash_mailing_list_id($this->number) == $_COOKIE[$this->id_base . '-' . $this->number] || false == $this->ns_mc_plugin->get_mcapi()
Just delete this and write in the brackets false.
This should resolve the issue and load the widget every time.