Help diagnosing a potential ram issue

Here's my issue, one particular game I play (Arma 2) will crash at random (this started recently around the exact same time as my bsod's). One time when it crashed I did get an error that said something along the lines of not enough memory or something like that. Also, I got "irql not less or equal" bsod's quite a few times. I really believe that it must be faulty ram (only based off what I read from others) but when I run memtest I don't seem to get any errors. Could it still be my ram and memtest just doesn't detect errors? Or is there something else you guys have in mind. Any help is greatly appreciated. I can try to get you any more info you need as long as you let me know what to do to get it. Thanks!