Feeds not validated on FeedBurner

I have problems with FeedBurner… they cannot validate my feed, i have problems on some lines:
If you go to:
https://feedvalidator.org/
and enter my feeds:
http//magarto.com/blog/feed/
http//magarto.com/blog/comments/feed/
there are problems and i cannot use it. I use an upgrade to wordpress 2.1
I have problems even if i use atom instead of RSS.
I have deactivate and activate the plugin for wordpress of feedburner but no results.

Can your help me? Is any line bad in wordpress?

Thanks