I used Winbox 3.x on Windows and it worked perfectly. When 4.x came out, I decided to try it, and when I opened it, it would immediately close. A process would appear in Task Manager and then immediately close. Now 3.x has stopped working for me too, and I don't understand what's going on. It also started closing when I clicked the Connect button. I have a Mac, and version 4.x works perfectly there and connects without any problems.