[horde] Horde 3.2.2 SQL SessionHandler Error

[Laura McCord]

I upgraded our horde installation last Thursday and everything has been 
going great until last night. All of a sudden we started receiving the 
following error in the logs:

Sep 30 23:00:21 HORDE [error] [horde] Could not connect to database for 
SQL SessionHandler. [pid 31393 on line 157 of 
"/srv/www/htdocs/horde/lib/Horde/SessionHandler.php"]

Then, we received the messages following the above:

Sep 30 23:00:26 HORDE [error] [imp] DB Error: connect failed:  
[nativecode=Host 'webmail.university.edu' is blocked because of many 
connection errors; unblock with 'mysqladmin flush-hosts'] ** 
mysql(mysql)://horde:PASSWORD at tcp+ipaddress:3306/horde?persistent=&charset=iso-8859-1&splitread=&table=horde_prefs&driverconfig=horde&umask=63 
[pid 31369 on line 1 38 of "/srv/www/htdocs/horde/lib/Horde/Prefs/sql.php"]

Does anyone know what may have sprung this or have some insight on where 
I should look to investigate?

Thanks.