Waah, Dave the Magician!
I uninstalled it and restarted my pc, started gunz and it has successfully started.
But now that we know it is bitdefender causing the problem, what should I do? About being my pc without Antiviurs I mean.
By the way, reinstalling Bitdefender taking a lot of time and idk why, even when installing it for the first time. And even sometimes it crashes before done installing :-\
Which means if you asked me to reinstall it, I may not reply until tomorrow cuz its already 22:10 here...