KStudio Project Manager does not start: Runtime Error: .NET Runtime Exception

[3d-labor]

Since I switched to Windows 11, I have the following error message when call KStudio Project Manager. The program does not start after that. I have tried several times to reinstall this program, I have also reinstalled 3D Studio Max 2026.2 and the support from CarStudio has tried to help me very knowledgeably even with taken over my PC eveb with a remote tool to inspect my PC. Unfortunately without success. Since I am certainly not the only one who has recently switched to Windows 11 and who also uses KStudio Project Manager, I would like to know if someone else also had this problem and if he was able to solve it. I have to say that I have installed Windows 11 over the existing Windows 10 installation and that I was very satisfied that in all other points the system is very stable and runs without any other error messages.
The error message reads as follows:
— Runtime Error: .NET Runtime Exception: Common Language Runtime Detected an Invalid Program
— File name: C:\Users\Turner\AppData\Local\Autodesk\3dsMax\2026 – 64bit\ENU\scripts\Kstudio\ProjectManager_3\Main.mse
— Line number: 326

[miauuuu]

Have you asked the creators of Project Manager about this issue?

[3d-labor]

Yes, I did so. I wrote you a mail regarding that topic. Please see your mail inbox.

[3d-Kstudio · Accepted solution]

Hello 

That’s actually an important clue — installing Windows 11 over an existing Windows 10 setup can sometimes leave behind registry entries or security policies that affect how .NET assemblies load.

You can try reinstalling or repairing the .NET

The issue not with Project Manager itself, but with leftover permissions or blocked libraries from the previous Windows installation.

Since you upgraded from Windows 10 to 11, some .NET components might not have been fully replaced during the upgrade, and this can cause the “Common Language Runtime detected an invalid program” error.

Do next to reinstall:

1. Open Control Panel → Programs and Features → Turn Windows features on or off

2. Uncheck .NET Framework 3.5 and .NET Framework 4.8 Advanced Services, then reboot.

3. After reboot, re-enable both components and reboot agan.

This will force Windows to rebuild the .NET runtime libraries.

[3d-labor]

Thank you for this answer. After I had completely uninstalled and reinstalled 3D Studio Max, the ProjectManager also ran again. I want to expressly thank Oleksandr from KStudio for his very engaged help. He took a lot of time for me. The only thing I can do is that I highly recommend his great tool ProjectManager to everyone. After working over 5 years with the ProjectManager I don´t know how I was able to work without it before.

[3d-Kstudio]

Thank you so much, your kind words mean a lot!

It was a pleasure helping you, and your feedback truly motivates us to keep improving the tool further.
Wishing you many successful projects ahead — and thank you again for your trust and support!