This is happened to me twice now, causing me to have to not uninstall dayz, but uninstall steam entirely. I've lost my steam library twice to this glitch because i really want to be able to alpha test this game.
That being said, randomly, out of no where- DayZ will decide it can't load any more. I installed it one time, worked great for a week. One night, couldn't load it. No errors, nothing. Steam just causes my pc to think for a second and no results. It's not in the windows task manager or available in the processes.
Its as if I never attempted to load the game in the first place. Uninstalling dayz doesn't fix this. Uninstalling steam and reinstalling it has been the only fix so far (even deleting folders within steam wont help)