nbill runtime error

[makuk]

Nbill has been running fine but now that my customers 2nd subscription payments are coming through, sometimes I receive the following error by email.

This error does not seem to come through with every subscription:

Could you please advise what the problem is, domain replaced with xxxxxx

Thanks

Billing Version:
Service Pack:
Domain: http://www.xxxxxxx.com
Date/Time: 02-May-2010 01:05:21 pm
IP Address: 66.211.170.66
Page: http://www.xxxxxx.com/index.php?option=com_nbill&action=gateway&task=ipn&gateway=paypal
Referrer:
Error Log ID: 13
Error Message: PHP Temp directory not found or not writable ('') - invoice attachment could not be saved.
File Name: /var/www/vhosts/xxxxxxxx.com/httpdocs/administrator/components/com_nbill/framework/classes/nbill.email.class.php
Line Number: 0
PHP Version (and OS): 5.2.12 (Linux)

[netshine]

Some of your clients have their email invoice option set to send the invoice to them as an attachment. However, the attachment cannot be created because your PHP temp directory is not set or not writable. You need to ask your hosting company to make sure that the user PHP runs under on your account is able to write to the PHP temp directory.