Same problem.

Okay I was able to start the game by going into program files and opening dayz.exe. But after joining a server battle eye tried to update and now DayZ wont open at all. I think there is something wrong with the dayz_be.exe or dayz.exe. I say this because for a brief second while battle eye was updating it said to launch dayz through steam or dayz_be.exe with launch parameters like 0 1 or something. So I think battle eye is the blame for this.

Hi AdamantorPL and sorry to hear about your friend's trouble.
Please tell him to try launching the game without any parameters (e.g. -nosplash and similar) if he is currently using some.
Also, please attach the files from his C:\Users\<Name>\AppData\Local\DayZ\ folder to this ticket in a .rar.
Regards,
Andy

He usually lauch launch game without parameters, later he tried -windowed (didn't worked). I will attach the files ASAP (prob. in the evening, when he will be online)

RAR archive uploaded.

Try this:

I HAVE FIXED IT!

I went into C:\Program Files (x86)\Common Files\ and deleted the BattlEye folder.

Next I disabled my Anti Virus and Firewall.
I couldn't turn off windows firewall so I added a rule for DayZ_BE.exe and allowed all connections.

Now I can start DayZ and BattlEye installs and the game works!

WORKS!
Thank you very much! :D
Ticket can be closed :)

Same problem again, but reinstalling BE doesn't work now :/

i have the same problem as you.. nothing helps..