[imp] Why is horde not logging anything

[MaxM]

I have logging set to enabled in horde.php and the file is /tmp/horde.log

$conf['log']['type'] = 'file';
$conf['log']['name'] = '/tmp/horde.log';
$conf['log']['priority'] = LOG_DEBUG;

But it still does not log anything ... even when there are problems galore.

I am running Horde 2.1 and IMP 3.1

Thanks.