FS9 ntdll.dll crash

Hi,

I've been going around the houses for some time trying to find the cause of an ntdll.dll error. It happens on FS9 usually between 15mins to one hour after loading a flight (but sometimes longer). It can take place at any location or time of day. I've tried disabling add ons, ai traffic and most recently a clean reinstall of FS9 using the late Opa Marshall's reinstallation guide to ensure there are no remnants of my previous install. I've run chkdsk, reg checkers and checked BIOS settings but nothing seems to work. I have previously run FS9 on this system for about 4 years flawlessly. The only hardware change in a graphics card upgrade to a 970gtx.

This is the only thing I can think of that has changed that could be causing the crash. I've tried the latest drivers, and older drivers with no success (using the guru3d driver uninstall tool). All other applications and games are working fine so I'm thinking it has to be something to do with how fs9 is interacting with my machine rather than a hardware problem. The exception code on the ntdll.dll crash is 0x4000001f. This seems different from the more common c000005 code that I've seen reported on many FS forums. I have no idea what these codes mean or represent but I'm hoping someone here could shed some light and possible give me some clues to solving this frustrating problem.

I'm considering putting the old graphics card back in and seeing if the ntdll.dll crash remains. Thanks for any help.