Install failed when changing ampwebroot


I’m trying to install the 2.10 freepbx version (i already install serveral older freepbx) but the install_amp failed with many of these errors :

Checking dashboard… PHP Fatal error: require_once(): Failed opening required ‘/var/www/html/admin/helpers/Email.php’ (include_path=’.:/usr/share/php:/usr/share/pear’) in /var/www/admin/ on line 137
dependencies pending

The begining of the install works (files are copy to /var/www), but it failed at the "Generating Configurations.conf"
I have just change the “webroot” to /var/www/ and doing this install on debian squeeze.

Do i miss something or is it a know bug ?