I've been playing some Blade and Soul lately and every 15 or 20 minutes my game has been randomly crashing. Updating drivers didn't fix the problem, nor did rebooting. After some Googling, I believe I found the culprit.

Blade & Soul's anti hack shield program nProtect seems to be a bit too overzealous in misidentifying potential hacking tools. Certain programs and processes can interfere with it and cause a crash. What fixed my crashing problem was closing the following 2 processes: "Razer Chroma SDK Service" and "Razer Game Scanner Service". So if you have these two processes running, bring up your task manager (ctrl+alt delete->Task Manager), find them and hit "end task". Sometimes these processes will keep rebooting themselves, so you may need to uninstall them to keep them from interfering with your game. Neither of these 2 processes are required to operate any of your Razer gear anyway, so don't worry about closing them out.

Making sure these 2 processes weren't running before I booted up Blade & Soul fixed my crashing problem, but it's not the silver bullet for everyone. So if you don't have these processes running but still experience crashes, try closing out of everything before launching the game. Close all unnecessary processes in the task manager too, as one or more of them may be interfering with the game. It's definitely upsetting to see the 2016 launch of the U.S. version plagued by these crashing issues. You'd think they ironed out all of these bugs in the 3+ years the game has been available in South Korea.

If you find any other processes that conflict with the game, share them in the comments below to help out other users!

Edit: The folks over at NCSoft suggested this fix as well as an alternative to disabling these processes:

We have been able to identify the issue that is causing the game client to crash upon attempting to log in. If you are using a Chroma Keyboard, running Razer Synapse, or Razer Chroma SDK Core Components software, you will need to modify the ClientConfiguration.xml file. To do this, first navigate to “MyDocuments\BnS\NCWEST”

Once in the NCWEST folder you should see the ClientConfiguration

Right click the ClientConfiguration file and select Edit

After selecting Edit you need to locate the following line <option name='use-chroma-keyboard' value='y'/>

Change the value from Y to N and then Save and Close. You should now be able to fully log into the game client. Please keep in mind, if you are receiving error 4049 as well, you will need to restart your PC after making these changes before you will be able to login.