Well it might be
Can you please check your /includes/config.php for this line and tell us what the value is?
If the value is 1 try setting it to 0
Code:
// ****** MASTER DATABASE PERSISTENT CONNECTIONS ******
// This option allows you to turn persistent connections to MySQL on or off.
// The difference in performance is negligible for all but the largest boards.
// If you are unsure what this should be, leave it off. (0 = off; 1 = on)
$config['MasterServer']['usepconnect'] = 0;