hi. i had the same issue as you which is mainly connected to the drivers of geforce-cards i think. i know 2 ways to get out of your misery. the short-term-version is to use this trick here: http://forums.dayzgame.com/index.php?/topic/56764-shift-flush-doesnt-do-anything/ and the long-term-version is to install an older driver for your graphics card (which solved the problem for me instantly). i used a pretty old driver though btw: some say its related to the graphics-memory-option in game. i personally didnt experienced a difference from setting it to my actual size or set it on "auto".