Weird. I'm not having this issue, but I know there were updates for Arma 2 and DayZ Launcher a couple days ago. I would try seeing if you can update or reinstall DayZ Launcher, then in DayZ Launcher, make sure that your files are not corrupted. Then check if Arma 2 has been updated and the files have been verified through Steam.
Also, one of the recent Steam updates sends a launch confirmation message when launching the game through DayZ Launcher. I would check to see if you're running the latest version of Steam.
Hope that works. Good luck.