Hello, welcome to the Pro forum and thanks for using our software.
The problem of the related post was caused by a custom patch that we sent to the user, so the fix is not applicable here.
In this case, it would be an installation issue. Please try this:
- Close Max.
- Delete the file <maxdir>\NVIDIA\shaders_autoload\mentalray\shaders\FShader3.dll
- Delete the file <maxdir>\plugins\ForestPackPro.dlo
- Reinstall Forest
Hopefully, that should solve the problem.