I have put a link in to show you the problem as i think its the easyest way to explain the problem and have tried to explain below for you as well
https://vimeo.com/152670048 password : canon
Basically you turn on the camera in mode M and then the MENU button and nothing happens you have to switch in to one of the modes below M on the functions dile and then back to M and you can access the MENU.
Once in the MENU when you scroll the main dial the green will cut out and you will have to do the same process again to get it to work.
You can start the camera in Auto mode and its all works fine then when you go back to M the problem starts again with the screen cutting out when you use the Main Dial.
i have put Magic Lantern Firmware 1.2.3 i know i know not a good plan but hay such is life. This was done 8 mouths ago and had had no problems.