Update: I've finally figured out what was wrong. It would seems that was a false positive from BattlEye, triggered by some process that I couldn't identify, even now. I'll explain my situation in case that helps someone in the future.
What happened was, I was playing on an Aion private server. Apparently, that particular server starts some process or service that triggered Black desert's anticheat and now APB's BattlEye. So whenever I start a session on that server, I'm forced to restart my PC to be able to play APB .. or BDO, or any game whose anticheat gets triggered by that process.
Thanks guys for your time and help. @MrsHappyPenguin TIL something new. That would certainly come handy when I need to know which process use what file. Thank you all.