Posts are not validating in feedburner

I am trying to get validation of the feedburner site from google because another program we use for email services, MailChimp, needs a valid RSS feed for use. If I press on the RSS icon on my site, it shows all the posts. However, when I use the command below, I get errors in formatting. Click on the feedvalidator link below and it will show you the problems. I have researched everything, installed a Fix RSS plugin, etc. but I obviously have no control on the formatting of this feed. Could you please point me in the right direction?

http://feedvalidator.org/check.cgi?url=http%3a%2f%2ffeeds.feedburner.com%2fOmniallinfinitude

Thanks,
Greg