I assume you already checked to make sure config.php does not actually echo or print anything to the buffer!
Look at your closing ?>. Is there a blank line after it? I've seen this cause the problem you describe. Delete anything after the closing tag. Also, if you are using PHP on Linux, make sure your files use Linux style line endings.
No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.