Header error on wp-admin after moving wordpress

Hello,
Im trying to move my wordpress install from one hosting provider to another. No change of url, i moved my files, my database and edited wp-config.php. The site works fine, but when i try to enter wp-admin i get error:
Warning: Cannot modify header information – headers already sent by (output started at public_html/wp-config.php:1) in /public_html/wp-includes/pluggable.php on line 881
wp-config has been double check to ensure nothing is before <?php.
Any ideas?