It solves two problems.
Firstly, it helps those whose game hangs on a black screen for a long time when launched. (I have Win7, and the game often only launched on the second or third try. A message appears: "An error occurred. Please reinstall the application. If the error repeats, contact technical support.")
Secondly, it fixes the bug in the second campaign.
Let's rejoice because there is a solution; to do this, you need to:
1) In the folder C:\Users\User Name\My Documents\Might & Magic Heroes VI\User, open the file "ProfileData" (in my case, it was in the Administrator directory).
2) Find the parameter gfx_InvalidateShaderCache and change the value from true to false.
I'll tell you right away that I didn't have this code at all; I just added it like this:
false
Good luck to everyone! :smile44: