[BlueOnyx:26430] Open_basedir errors

[Colin Jack]

I appreciate this is pretty much a noob question but I am struggling to resolve it!
Any guidance would be appreciated. 

We have a customer with a vsite that includes a PHP script to flush their database regularly to clear old records.
The script works fine if run from a web browser (http://www.domain.com/cron.php) but when I try and run as a cron job I get open_basedir errors:

PHP Warning:  include(): open_basedir restriction in effect. File(/home/.sites/90/site26/web/control/cfg.php) is not within the allowed path(s)

It runs okay from the website so wondered where the problem is. 
I have fiddled about a bit without success.

5209R

I have created a file in cron.daily containing the following:

/usr/bin/php /home/.sites/90/site26/web/cron.php

Where to go next please.

Thanks

Colin