True Image Home 2011 ftp backup chains cannot be deleted?

I'm using True Image Home 2011 (successfully) to do weekly backups. I've set it up to keep only one backup chain. I'm backup up to an ftp server. The new chain gets created appropriately, but the old chains do not go away. I can't delete them by selecting them and telling the program to delete them.

I've had to resort to editing the XML in the archives.xml file, and deleteing the files by hand. What Am I doing wrong?