parsing PHP in header template

[WeBBy]

First, I have searched the forums, been through many pages, and am still having problems - I must be doing something really STUPID. Can you see what I am doing wrong?

VB 3.0.7 (unhacked - ATM)

Header template:
<!--\HEADER-->
<!--NAVIGATION-->
$navigation
<!--NAVIGATION-->
<!--SPACERS-->

phpinclude_start:

ob_start();
include('/home/xxxx/www/templates/navigation.php');
$navigation = ob_get_contents();
ob_end_clean();

The include file has the full path. Have tried with other paths as well. Navigation.php is simple an image at this stage as I have not added the navigation:

../templates/navigation.php (relative location to forum)

<!--NAVIGATION-->
<TR>
<TD COLSPAN=7><IMG SRC="http://www.xxx.com/images/layout_10.jpg" WIDTH=780 HEIGHT=46></TD></TR>
<!--NAVIGATION-->

So the php script can't be interferring with anything

Any ideas as to why thsi bloody thingy won't work woiuld be appreciated

Thanx