I just caught the tail end of this, and decided to do a little more trouble shooting.
I turned my A/V software off and got a different error message this time - same C000005 error, but instead of "App Crash" the Problem Event Name this time was BEX Error. A little more research and it pointed to Data Execution Prevention (DEP). I went in and added both client.exe and mabinogi.exe to the exceptions for DEP and VIOLA! Abyss is working again. Woooo! Thanks for the tip off Blade. Even though it wasn't the A/V blocking it, I still managed to find a fix by turning it off. LOL
Holy crap, mate. You made me remember something... DEP was the problem!
The thing was, each time I reinstall Windows, when I go through my rounds of installing all of my programs and games, and migrate all of my settings files and install any OS modifications and such, adding C:\Nexon\Mabinogi.exe and Client.exe to DEP exceptions have always been part of my routine. It's one of those things that you just set, and then forget you ever had to do it in the first place.
After destind's post, I decided to try adding the client as an exception. As it turns out... I already had Mabinogi.exe and Client.exe in my DEP exceptions. I had just forgotten about them.
So, seeing how Nexon
forced us all to change our Mabinogi directory to some other directory that ends in \appdata\, that must have screwed with DEP's exceptions, since it's looking for Client.exe in your previous "[driveletter]:\folder\Mabinogi\" directory
Anyone else having crashing issues with Abyss, go into your DEP settings and ideally
remove the old instances of Mabinogi.exe AND Client.exe from the lists,
then add Client.exe from your
new appdata directory. There is no need to add Mabinogi.exe from the new directory because that is the executable for the old launcher, which is now intentionally
broken, thanks to Nexon being completely incompetent, and always making
stupid decisions.