pluggable.php errors

i get this error when doing things in the admin panel [ie: publishing posts]:

Warning: Cannot modify header information – headers already sent by (output started at /home2/takingov/public_html/wp-content/themes/illacrimo/functions.php:24) in /home2/takingov/public_html/wp-includes/pluggable.php on line 391

i just upgraded to 2.3.1 and i still get this error. I currently have NO plugins activated. the only ones in the directory are ‘askimet’ and ‘hello dolly’, which came with the install of wp.

I cannot just reinstall either. i try to export my posts to an xml file and i get that same error message.

any ideas on how the hell i can fix this problem. it truly is a pain in the ass.

thanks.