This is a very annoying bug that I encountered twice, once during the main campaign and once during the extension campaign.
I saved the game and then when I tried to load it it crashes on a pure virtual funciton call in the Visual .NET C++ library.
I have attached the extension save file as I have overwritten the default campaign one that was crashing:
Here is the bug image when it occurs
Also note that my steam installation is on a separate drive than my OS. and so my save game for this game are also not on the OS drive.
I am playing on a windows 7 64bit, service pack 1 family premium edition.
RAM : 16go of DDR3.
CPU: intel core i7-2700K @ 3.5GHz
GPU: NVIDIA GEFORCE GTX 970 with latest drivers
Thank you for correcting this bug, it is very annoying as I have to redo the whole level every time it happens.
Customer support service by UserEcho