Akismet Configuration Error

Hi,

I just activated akismet and went throught the configuration. I put the API code in the akismet.php file by hand. When trying to check the “Automatically discard spam comments on posts older than a month” box i get the following error:

Warning: Cannot modify header information – headers already sent by (output started at /home/sandulli/public_html/sgblog/wp-admin/admin-header.php:16) in /home/sandulli/public_html/sgblog/wp-includes/functions.php on line 1219

Any Idea’s how to fix?

Thnaks in advance for any assistance.

Chris