How do you check multifield unique keys in DataMan?

[Jaxel]

So I'm using the DataMan, and it seems pretty simple... however, I am having problems checking for unique values... This is one of my VF_METHOD functions...

function verify_serviceVAL(&$serviceVAL)
{
	$serviceID = $this->fetch_field('serviceID');

	if (!$media = $this->dbobject->query_first("
		SELECT * FROM " . TABLE_PREFIX . "media AS media
		WHERE serviceVAL = '" . $serviceVAL . "'
			AND serviceID = '" . $serviceID . "'
	"))
	{
		$this->error('media_already_exists');
		return false;
	}

	return true;
}

Theoretically, with this code, if the combined values for serviceVAL and serviceID are not unique, it should return an error. However, it doesn't seem to be working for me, and I keep getting a database error...

Database error in vBulletin 4.0.2:

Invalid SQL:
INSERT INTO media
	(categoryID, userID, serviceID, serviceVAL, username, title, description, length, dateline)
VALUES
	(2, 1, 2, '9953368', 'Jaxel', 'Nature by Numbers', 'A SHORT MOVIE INSPIRED ON NUMBERS', 224, 1270164500);

MySQL Error   : Duplicate entry '2-9953368' for key 2
Error Number  : 1062

In my table, I have a UNIQUE KEY called "service" for "serviceID, serviceVAL"; which is why its posting the error. However, the code in the datamanager I have above should prevent this hard error from showing it up. But its not working...

Am I doing something wrong?

--------------- Added [DATE]1270165322[/DATE] at [TIME]1270165322[/TIME] ---------------

Also, quick question about data managers... what is the difference between REQ_NO and REQ_AUTO; the manual doesn't really explain a difference.