I was using DX11 beta daily since the release last month with only seldom in-game crashes, which seemed to stabilize if I lowered the animation settings to the lowest. Performance-wise, I was consistently getting slightly improved FPS and with running slightly higher graphic settings with the DX11 rendering beta on my old Alienware 13 R2 laptop (note that I can't run at highest settings with this old laptop, but most settings could still be tuned up with DX11).
Tonight (Tue Oct 13) was a different story. In the morning, everything was as normal, but in the evening (EST), I was getting a crash on login that I never saw before "Exception c0000005 Memory At address 00000000 000000000 could not be read....". I started troubleshooting the wrong way using old developer notes, none of which worked (i.e., I tried the .exe with each of -repair, -dx9, -windowed), cleared the GW folder in the temp cache, did a clean boot from msconfig disabling all non-Microsoft services on startup and disabled other excess tasks from task manager) and none of these incremental changes would get me to the character selection screen as the crash window with the above message would pop up immediately after initiating 'play' on the login menu.
The only way I could surpass this was to run my PC off same mode - network, and this allowed me to start up the game with the normal .exe file. While graphics and performance is completely shot in safe mode, at least I was able to login now and change the settings, which I promptly turned off DX11 (and set to windowed to fullscreen). I believe a developer had made some post to this earlier, but I just want to note that this error is new to me as I had not encountered over the last few weeks of DX11 beta testing (and I login everyday), and because it occurs right at the login screen, this may actually prevent testers to enter the game if their settings was already at DX11. Hopefully this gets patched up as I did not have this issue prior to today