Warning: cannot modify header information (another one)

Hello
This is my first installation, but I have tried a dozen times yet and asked for advice to persons who know how to do it. Also read a lot in the forums and this http://codex.wordpress.org/Answers-Troubleshooting#Headers_already_sent
I have edited wp-config.php, but I did not find any spaces or break lines. The message remains:

Warning: Cannot modify header information – headers already sent by (output started at /homepages/17/d365599058/htdocs/wp-config.php:1) in /homepages/17/d365599058/htdocs/wp-admin/install.php on line 54

What am I doing wrong? Please help…