Hi David,
you can check the validity of your RSS at any time using these resources:
http://feedvalidator.org/
http://validator.w3.org/feed/
They both provide extensive analysis of the errors your feed contains.
In this particular case your feeds are invalid because of using the feature "geotagging" of Blogger platform. More about this feature:
http://mapperz.blogspot.com/2008/12/blogger-gets-geotagging-georss-support.html
Unfortunately, "a geotag cannot be removed from a post once it has been saved," so you need to repost every post that is geotagged to get rid of this error and make your feed interoperable.