In addition to the change that Willi noted in his initial post on line 18 of diagnostic.php you would update the Connections/PowerMailerConnection.php file and add the code to the top of the page:
<?php
if (function_exists('mysql_set_charset') === false) {
//Note: This function requires MySQL 5.0.7 or later.
function mysql_set_charset($charset, $link_identifier = null)
{
if ($link_identifier == null) {
return mysql_query('SET CHARACTER SET "'.$charset.'"');
} else {
return mysql_query('SET CHARACTER SET "'.$charset.'"', $link_identifier);
}
}
}
?>
that should fix the problem in older versions of PHP.