There were SQL errors in the cart_reminder_install.php (latest version).

On line 46:
Code:
$sql = "UPDATE `".DB_PREFIX."configuration_group` SET `sort_order` = $last_id WHERE `configuration_group_id`=";
The "configuration_group_id" variable isn't passed into the statement. I commented this out.

In addition to that, the statements that follow do not append the DB_PREFIX to the configuration table.

i.e.
Code:
$sql = "INSERT INTO configuration ...
should be
Code:
$sql = "INSERT INTO `".DB_PREFIX."configuration` ...
Thanks for all your help!