My 550D camere is frozen when stop recording fps override video. Sometimes. I use 720p, and change frame rate to 25 fps with FPS Override function. Video bitrate is 0.6 or 0.7 CBR.
Tipically crashing in long time video, and lost the video file. e.g. 45 min. or 25 min.
This problem is not occurs in 600D, same ML version.
Magic Lantern version : Nightly.2014May13.550D109