After several test we had in private with laking, it has been established the crash in terrain.dll doesn't have anything to do with our scenery, and it happens ONLY when using OrbX, and user laking confirmed to me the crashes stopped if OrbX is disabled.
Thats interesting as this problem seems to occur with both the FSDT and the Aerosoft LSGG scenery.
Which part of Orbx is causing the issue? Did you deactivate openLC, Base or everything? Has this been passed on to Orbx, as I can't find anything related on their forums?
I am currently avoiding LSGG as I too have CTD, especially when approaching from the south, between CBY and GVA VOR's. I too have Orbx packages installed.
Edit: I even had a CTD just flying past LSGG on a flight from LSZH to LEMG.