Hi I'm Apple!
I've been playing this since January since before the 64-bit version client was launched so I was really happy when it came out. I enjoyed for a few days and then it simple puffed, went bad, errors and errors, game not opening or closing after a while for nothing, or bad fps til it simply wouldn't open anymore! I know these are issues for a lot of people so I tell u what I did this time and what could be the answer!
So there are 2 possible things: the update itself, windows' FTH feature.
Every time the game updated I was able to open the game or get close to it in the first try or tries, then it would stop working. Take note of that.
This is the explanation for FTH: "The Fault Tolerant Heap (FTH) is a subsystem of Windows 7 responsible for monitoring application crashes and autonomously applying mitigations to prevent future crashes on a per application basis. For the vast majority of users, FTH will function with no need for intervention or change on their part. However, in some cases, application developers and software testers may need to override the default behavior of this system." BTW this feature is on windows 8 and 10 too. I use windows 10.
Here is a guide on how to disable it: https://coronarenderer.freshdesk.com/support/solutions/articles/5000678431-windows-enabled-fault-tolerant-heap-for-3dsmax-or-dependent-processes-this-may-have-severe-perform
Now u will see a lot of methods to do it in there, I haven't tried all of them to see what works and what doesn't, I tell u what I did.
One of the methods lets u exclude an application alone rather than disabling the feature, but when I did what the guide said about finding the application in the logs or even in the keys in regedit I didn't find anything, meaning 2 things: the game wasn't there, no other app was using it; so what I thought is simply that the issue is not with it fixing, but rather, trying to fix something in the 64-bit client, that isn't there!
So I disabled the FTH entirely. I did the regedit part, and the cmd part (which has to be in admin mode), also I checked the 'STATE' key to see if something was there. Now remember what I said about update? Well if u tried opening the 64-bit client after the game updated I don't know if it works or not, try it out. If you don't manage to get in, try waiting for the update on 26th and do these tricks again, especially the cmd part and try to open it!
It's been working for 2 days for me, no crashes, no bad fps, no bad loading time it's gorgeous!
Apples anyone? >.<