Having the same issue. Started randomly a couple of days ago after 30 hours played with no issues. Textures load very slowly and after a few minutes in game the screen goes black and my desktop displays. I then have to minimize DayZ and force close it.
Using a 770 (NVidia) with 331.82 drivers (just updated them, was having same issue with previous drivers)
AMD Phenom II 1090T Black Edition
8 GB RAM
No overclocking being done.