Before you posted the above did you check?
line 76 is ‘?>’ and ends in a line break followed by line 77.
How do you know your feeds are valid? did you use a validator? http://feedvalidator.org/
I found this error with a clean install and have even checked it again by re downloading it to make sure I did not invalidate in the process of instalment.
“Check your wp-config.php file for blank lines outside of <? and ?> bracketed sections.”
http://feedvalidator.org/docs/error/WPBlankLine.html
This is issue is not resolved.
