I'm not sure If me offering a solution would be frowned upon or welcomed, but I know it's frustrating when waiting for a reply with these sorts of things as well as those trying to help having lots of reports to deal with. So I'll offer it anyways and see if it helps. Feel free to ignore it though Killslim :D
I would suggest
Close down the game.
Go into your documents: Windows button>documents>dayz and then delete the DayZ.cfg file. Then when you restart the game, the cfg file will renew itself and all settings will be at bare minimum when u go back into game. When in game go to configure, video,USER INTERFACE. Change the resolution to the one u want. Adjust the other 2 also if needed. Then go back to the other video settings and adjust all your settings like shadows.. textures and on and on to what you want. Then CLOSE the game again. Restart it and then go back into configure,video, and there change the resolution on that part also to the one u want. Hopefully that will fix it and you'll get the resolution you want.
Just remember the steps about first changing resolution in the user interface section first, restarting and then after that changing the resolution settings on just the Video settings page. I say this because on one of my pc's I play it on I also had a problem with it. This is the only way i found to fix it. Best of luck and I hope it helps. If not then Soz :D