RSS Feed not well formed error

<b>Warning</b>: Cannot modify header information – headers already sent by (output started at /nfs/c03/h03/mnt/52741/domains/blog.elliotrock.com/html/wp-config.php:64) in <b>/nfs/c03/h03/mnt/52741/domains/blog.elliotrock.com/html/wp-includes/pluggable.php</b> on line <b>850</b>

The above is getting tagged onto the start of the RSS2 feed from my blog.

Any ideas? Seems the world is falling apart on me ATM