header error

Can anyone tell me how to correct the following error?

Warning: Cannot modify header information - headers already sent by (output started at /home/communit/public_html/inc/utils.inc.php:1658) in /home/communit/public_html/inc/design.inc.php on line 958

Usually, when I receive these errors, it is because I was installing a mod and made a mistake somwhere along the way.  Have you recently installed any mod ???