you might want to try reinstalling battlEye via the steam menu. Check out this thread for more details. http://dayzmod.com/forum/showthread.php?tid=269&pid=17508#pid17508
Found answer in another thread... Check out: http://dayzmod.com/forum/showthread.php?tid=269&pid=17508#pid17508 In a nutshell? Reinstall BattlEye via the steam menu.