Can you post the warnings to this thread?

It looks like sessions.php and page_header.php are each trying to send header information with the header() function but failing because something on line 19 of config.php is outputting spaces or newlines.

Whenever you try to send header information, you must ensure that no previous function calls or scripts have sent anything, even whitespace. Make sure that there are no echo or other print statements in config.php and make sure there are no spaces or newlines on either side of the <?php ?> tags.

For example:
// beginning of config.php

<?php
$somevariable = 1;
// other stuff here
?>

// end of config.php

This will cause the errors you're getting, because there are spaces and newlines in the script that the server will interprete and output. The following is okay:<?php
$somevariable = 1;
// other stuff here
?>