[Plugin FeedSmith]: Cannot change wrong URL

When I copied the URL from FeedBurner I copied also a blank:

http://feeds.feedburner.com/ MySiteName

I change it to

http://feeds.feedburner.com/MySiteName

I tried this several times. I deactivated the plugin and reactivated it. But when I click on the article feed I’m always forwarded to

http://feeds.feedburner.com/ MySiteName

In Firefox I get: You must provide a feed uri
Error 400
In Google Chrome I do not see where I’m forwarded to. I do get a result but it is not recognized by the feed reader. But it seems to be the source of the RSS feed.

I also added the correct URL for the comments feed. The comments feed works like expected (Firefox, Chrome).

Is there some kind of cache which caches the redirection URL. In the database I’ve only found the correctly spelled URL (without blank).