Bug? File is below active open_basedir setting, but not seen by php

[gecon]

Hello,

I'm dealing with a problem related to php and the open_basedir setting.
Running Plesk 8.0.1.

The error I'm getting when requesting a web page is is a typical: "open_basedir restriction in effect."
but there seems that this shouldn't happen, since the requested file is below the defined directories in open_basedir restriction.

Here are some details.

In file:
/var/www/vhosts/asite.com/conf/httpd.include

there is:

<IfModule sapi_apache2.c>
                php_admin_flag engine on
                php_admin_flag safe_mode off
                php_admin_value open_basedir "/var/www/vhosts/asite.com/httpdocs:/tmp"
 </IfModule>

and there isn't any vhost.conf file in:
/var/www/vhosts/asite.com/conf/

I'm requesting by using a browser the following:
http://www.asite.com/admin/index.php?action=products&sub=view
which gives the following error:

Warning: main() [function.main]: open_basedir restriction in effect.
File(/action_products_view.php) is not within the allowed path(s): (/var/www/vhosts/asite.com/httpdocs:/tmp) in /var/www/vhosts/asite.com/httpdocs/admin/modules/action_products.php on line 5
Warning: main() [function.include]: Failed opening 'action_products_view.php' for inclusion (include_path='.:') in /var/www/vhosts/asite.com/httpdocs/admin/modules/action_products.php on line 5

The line 5 of the php source code (file: /var/www/vhosts/asite.com/httpdocs/admin/modules/action_products.php) in which the warning is given is just a:

include("action_products_view.php");

and the file:
/var/www/vhosts/asite.com/httpdocs/admin/modules/action_products_view.php
exists (it is in the same directory with the file making the include and below the allowed paths in open_basedir).

What might be wrong?
From the warning it seems like the

include("action_products_view.php");

generates a requests for: /action_products_view.php
(in site's root directory) - not a relative to the existing request.

Has anyone seen this and fixed this?
I don't want to remove the open_basedir restriction (by setting it to 'none' or to '/'). Any ideas?

Thank you.