promethius (DayZ)

okay, so i just downloaded arma 2 co the other day. for the soul purpose of playing dayZ, but when i open up and try to get into a server i get horrible fps, and giant patches of white all over my screen does anyone know what is wrong? or how to fix it.

it happens on any server i join, and im not able to change any options for some reason, i tried changing to low quality and it wouldnt go off of normal