If I end playing a self created SP mission, which I have started before directly from the mission editor, you normally hit the ESC-Button and than klick the "Quit"-Button to return to the mission editor.
If you do it now, the games freeze everytime and I have to end it via the Windows Task-Manager.
This does not happened, if I start and end (as reported above) a saved SP mission directly from the main menue
Beside that MT works fine for me an I gain 10% more FPS.
Edit: Freeze also possible if I start mission from Main Menü.
BR Ulfrun