This might have been resolved somewhere else but I couldn't find anything in my search.
Basically the core channel elements description defaults to Mission which does not exist in Drupal 7.
I found this with regard to views:
"Remove the option to use the site mission for the RSS feed description"
So it could be a views issue instead.
The funny thing though is that I would have hoped that something they committed in December 18, 2010 to Views Dev would have managed to make it into the full release by now.
I thought to report it here first to confirm is it was a views fields issue or not.