Bug in 6.5.4.1 when you attempt to add a Marker, the Marker window opens with the Name field selected instead of the Comment/Description field. Also, you cannot 'tab' to the Comment/Description field. The only way to enter text in the Comment/Description field is by using the mouse. Previous versions and later versions of MC select the Comment/Description field automatically.
Having to use the mouse to select the Comment/Description field greatly slows down the process of adding Markers.