Don’t know if this adds in any way to the discussion so far. I too have been having the problem of some generators and titles “turning blue”. Can’t quite bring myself to refer to the problem as the blue screen of death!
I should have started at the end of this thread and worked back but didn’t. Having tried removing the various plist and pref files to no avail I reached the advice to remove files from user/library/application support/motion/presets/projects. There was only one file in the folder and removing it also worked for me.
The file removed was Broadcast HD 1080 copy.preset. I am in the UK so NTSC presets are not appropriate for me. The Motion 5 Preferences do not include a 1080 25fps Preset and so to create a default preset Motion 5 creates a copy of a selected preset in the existing set of defaults.
Having solved the problem with your aid I decided to dice with the blue screen of death again and created a new 1080 25fps default in Motion 5. Sure enough the problem recurred, remove the motion preset and all is well.
I hope that this may give some clue as to what may be causing the problem.