I was not having problems in 64bit until 2 days ago...
I was in Eden editor doing a simple mission (NPC's shooting at each others). When I started the mission I was having fps trouble so I restarted it but it did the same thing when it started (I had no lag in the Editor btw). I tought it had to do something with my RAM or CPU so I Alt+Tab to see if everything was ok but everything looked fine so I went back in the game to play but I had a black screen. I restarted my computer and launched Arma but unmoded this time, joined a random vanilla server to see if it fixed itself. I spawned my fps looked good but 10sec later I went down to 1fps. It was the first time that I had this issue so I restarted my computer again, launched Arma in 32bit this time and my fps was ok. Like I said before it never happened to me even when Arma was only in 32bit.
I have a report saved if needed.
