Unfortunately, that message means that FeedBurner consistently encounters "time out" states when trying to retrieve your source feed content. This means your web server isn't responding quickly enough to regular requests from our own feed poller, which requires a response within 10-15 seconds of initial contact. You may want to contact your hosting provider to ask them whether there is anything about your account or site configuration that might lead to slow response times to requests from FeedBurner.