There is an bug in Flock 0.7.8 on Windows (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.8) Gecko/20061109 Firefox/1.5.0.8 Flock/0.7.8). When you drag&drop all available widgets on the sidebar div and save changes, then you won't be able to drag&drop any widget back onto the 'available' div, what means that you won't be able to delete them from blog layout. I could delete them only when I've raised the number of rss widgets, and then they've appeared on the available div, so I could drag&drop sidebar widgets normally.