maybe helps, posting video of it (sometimes it's even worse):
http://www.twitch.tv/lapsa/c/3181292

this problem is like #1 in my priority list. most of all - I enjoy playing Arma as a sniper, slowly reckoning what's around me, waiting for my target. it's irritating when whole screen flickers (not to mention enemy soldiers walking through air, shielded by invisible terrain).

lurked around to dig some info and this looks promising:
http://outerra.blogspot.com/2009/08/logarithmic-z-buffer.html
(found on arma2 feedback tracker)

Not anything is terrible. Menu theme song is frickin awesome :)