Debugging an rss feed error (extra at the end)

Hi all,

Can someone suggest me how to go about debugging my RSS feed? (as in, how to find what is causing the error?)

Link:
http://www.r-bloggers.com/feed/
Validator:
http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fwww.r-bloggers.com%2Ffeed%2F

Thanks!