Não consigo acessar o /wp-admin

Olá,

Meu provedor de hospedagem mudou o PHP 5.2 para o 5.3 Fastcgi.

Depois disso, meus blogs estão com problema para acessar o /wp-admin.

Vejam:

Blog 1) Warning: Cannot modify header information – headers already sent by (output started at /home/microcredito/microcredito.blog.br/wp-config.php:1) in /home/microcredito/microcredito.blog.br/wp-includes/pluggable.php on line 881

Blog 2) Warning: session_start() [function.session-start]: Cannot send session cache limiter – headers already sent (output started at /home/unipress/unipress.blog.br/wp-config.php:1) in /home/unipress/unipress.blog.br/wp-content/plugins/yourls-wordpress-to-twitter/plugin.php on line 70

Warning: Cannot modify header information – headers already sent by (output started at /home/unipress/unipress.blog.br/wp-config.php:1) in /home/unipress/unipress.blog.br/wp-includes/pluggable.php on line 876

Como resolvo esse problema?