The 2 versions of the Dude need their own different Dude Client applications with matching version numbers. Between ROS v6.43.4 and v6.48 there’s been changes made to the Dude to cause some incompatibility between devices on different versions. ROS v6.45.9 has been reported to be the newest most stable version for the Dude prior to the changes.
http://forum.mikrotik.com/t/v6-46-4-stable-is-released/137189/1