Hello,
it is possible that some of your hardware is corrupted and is causing trouble under a full load. It is also possible that you have not experienced this with other games, Arma 3 more performance demanding than most of the today's games. I would suggest to run a couple of heavy benchmarks to see if the problems occur as well.
The most suitable for you could be:
http://unigine.com/products/heaven/
http://unigine.com/products/valley/
http://www.memtest.org/
Please run these benchmarks (at least one hour each without interruption) at highest possible settings. Then you will see if your hardware is showing incorrect behaviour under heavy stress or not.
Thank you very much.