the error is caused by blank lines between closing and opening php tags.
lines 4 - 6:
<?php require_once("../../webassist/database_management/wa_appbuilder_php.php"); ?>
<?php
should not have the the blank line at line 1:
<?php require_once("../../webassist/database_management/wa_appbuilder_php.php"); ?>
<?php
see this thread for more details on the headers already sent error:
http://www.webassist.com/forums/posts.php?id=19285