When you have raw video enabled and try to use magnification in live view a crash happens.
I have the same issue in my 550D.
It happens using Canon or ML live view
It happens in any resolution - Raw video and Raw video MLV
It gives Err 70
ML Nightly 2014 May 20
My workaround for this issue in my 550 is:
I rotate the upper dial to 'M' mode, zoom 10X, focus, get back to Movie
mode and shoot.
It's a pain... but sometimes 10X zoom is very useful for critical focusing