Kerbal Space Program

To reproduce:

1) Move to the map mode and select a vehicle that is in space, in orbit.
2) Click the orbit line and then click the "Add Maneuver" button that appears to create a maneuver node.
3) Notice in the lower left hand corner, the maneuver node editor, the "Delete Maneuver" button (red square with X in it) remains unlit and un-click-able.
4) Use the arrow button to move to the "Orbit" tab and then the other arrow button to move back to the Maneuver Node you just created. Notice the Delete Maneuver button is now lit and can be clicked.