Opencart headers probleem

[harriej]

Hallo, ik heb een header probleem:

line*174**Warning*: Cannot modify header information - headers already
sent by (output started at
/home/beesandb/public_html/shop/index.php:102)
in*/home/beesandb/public_html/shop/system/engine/controller.php*on
line*37**Warning*: Cannot modify header information - headers already
sent by (output started at
/home/beesandb/public_html/shop/index.php:102)
in*/home/beesandb/public_html/shop/system/engine/controller.php*on
line*38

controller.php:
line 38: header('Location: ' . str_replace(array('&', "\n", "\r"), array('&', '', ''), $url));

Iemand enig idee wat ik kan doen?
Thanks