Error Message

I have two problems. When i am updating my changes in my CSS in the editor the page becomes a blank white page with a error message that says: “Warning: Cannot modify header information – headers already sent by (output started at /home2/ab20887/public_html/wp-content/themes/vantage-child/functions.php:6) in /home2/ab20887/public_html/wp-includes/pluggable.php on line 1196”.
The other problem is that i cant search for themes, when clicking at “appearence – themes – add new” i get this message on the page: “An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums.”.
What should i do? I would think that these two problems have a connection. I am using a Vantage child theme and everything has been good for weeks until today. I am wondering also where this place is “/home2/ab20887/public_html/wp-includes/pluggable.php on line 1196”? I cant find it. When using other themes, i have no problems. Regards