I have burned my feeds in the feed burner (even before Google bought it). Later all my feeds are imported to Google servers by Google itself. Few days back i just deleted one of my feed and tried to create a feed with same id, but i failed. It was showing that id already exists.
I had a search on this and found that many have the same issue. Later i found a post in the Google groups, stating the same, i also posted my issue there. few days later got a reply that they fixed this issue.
So i tried and got that feed back. But still don’t know this is for the feeds posted on that post or for all.