Subfolders disappear after next sync in v7

Ever since I was forced to upgrade from v6 to version 7 all my subfolders under the Inbox have disappeared.  When I create a new one it disappears immediately after syncing.  I have Frontier mail (Yahoo! Mail powered).  The new subfolders do show up on the webmail, but not in the eM Client.  None of the new subfolders I create on webmail show up in eM Client.