I've had this happen twice on 0.57, it happened once before but it was a long time ago, maybe like 0.50 or something.
I'll describe it as best I can, its happened once while driving and once just after I killed another player (a truck was nearby and had driven it just minutes before) everything is normal, no lagging or anything like that and then suddenly the screen goes blue, like the base color of the sky in DayZ, a smokey blue, I can still hear ambient sounds and I can still hear people in my teamspeak but I can't do anything, I cannot Alt+Tab, Ctrl+Alt+Del, Ctrl+Shift+Exit, the only thing I can do is restart my PC. This only happens on DayZ and it doesn't seem to have any reason for happening, it doesn't happen under heavy load or anything like that, it happened once outside of Kamyshovo and once outside of Vyborg.