pluggable.php erros

i have been getting some strange errors lately, does anyone know how to fix these?

Warning: Cannot modify header information – headers already sent by (output started at /nfs/c07/h01/mnt/98885/domains/dev.aihscorp.org/html/wp-content/themes/aihs/functions.php:68) in /nfs/c07/h01/mnt/98885/domains/dev.aihscorp.org/html/wp-includes/pluggable.php on line 868

Warning: Cannot modify header information – headers already sent by (output started at /nfs/c07/h01/mnt/98885/domains/dev.aihscorp.org/html/wp-content/themes/aihs/functions.php:68) in /nfs/c07/h01/mnt/98885/domains/dev.aihscorp.org/html/wp-includes/pluggable.php on line 868