I'd guess you either have failing hardware or Nexon's anti-cheat [S]malware[/S] software is having a conflict with one of your drivers.
The first thing I'd check is if your RAM is OK: Windows 7 has a built-in memory diagnostic tool called...
Windows Memory Diagnostic. Locate it by typing it into the search field and run it. It'll reboot your computer and do the test. Default values should be fine. Results are a bit harder to find; you have to dig through Windows system logs for them. xd
From Computer Management (again, use Search to launch this), navigate here and do a Find on "memory" or something to check the log:
[Image: http://i.imgur.com/Oc5c82w.png]
Aside from that, it wouldn't hurt for you to check if all of your drivers are up to date. These are two good things you should be checking regardless of whether it actually solves your problem!
Running
sfc /verifyonly from command prompt (might need to run it with admin rights) to check system files integrity wouldn't hurt, either.
I suppose you could also analyze the Windows crash dump with WinDbg or something, which could give a hint as to what's causing the crash, but that can be a bit of a pain to
set up.