Warning: Cannot modify header information - headers already sent by (output started at /home/example.com/wp-content/themes/twentyten_subtheme/functions.php:2) in /home/example.com/wp-includes/pluggable.php on line 934
It sounds to me like there is an extra space somewhere in your code for it to be giving you this error. Make sure there is no extra space at the bottom of your functions.php file and any file included in there. Also, please remove all closing PHP tags from those same files as well. Hopefully that will solve the issue, otherwise you will have to dig deeper because essentially what it is doing is something is trying to output to the browser before it should be.