I found the answer to the blank line error when trying to submit your WordPress Blog to Feedburner or other blog cross post service like NetworkBlogs (at Facebook).
All you need is ‘Fix RSS Feed’ plugin – available from the WordPress Plugin Directory (http://wordpress.org/extend/plugins/fix-rss-feed/). You can also download it from the developer’s website (http://www.flyaga.info/).
There you go… Struggle no more. Another useful tip from http://www.martinkoss.com – have a great day.