Error in Guestbook... "Unblock" command

I've tried searching for an answer, but have found nothing. I've been runiing guestbook for a while now and haven't had any problems until now. I'm getting the following warning:

Warning: MySQL Connection Failed: Host 'cluster.mhp01.affinity.com' is blocked because of many connection errors. Unblock with 'mysqladmin flush-hosts' in /nfs/cust/7/30/52/425037/web/guestbook/lib/mysql.class.php on line 30

I'm not really sure how to fix this. Please help.

Thanks.

You need to speak to your hosts about it.