I'm getting this error message when trying to run the game. Any help would be appreciated.

Update: the problem seems to be solved by opening it in windows xp compatibilty mode. But only clicking the exe. The bug still persists on gog galaxy.

Get the same, Work when launching with "nwmain.exe" but not with the GoG Shortcut

Looks like it could be an issue with the C++ Runtimes. You could try installing the latest C++ Redistributable and see if that fixes it.

It's a bug with amd/ati graphics cards there's nothing we can do about it. I got this from the customer support:
"Unfortunately, this is a known issue that occurs when you are trying to launch Neverwinter Nights Diamond on a computer that has AMD/ATI Graphics Device.
Please navigate to the main folder where the game is installed(default: C:\GOG Games\NWN Diamond), right-click on nwmain.exe and choose: create shortcut.
After that, please right-click on a shortcut and press: run as administrator.
If that does not help, then please right-click on nwmain.exe, choose rename and rename this file to something different. After that, please try to launch the game from this .exe"
So yeah, we'll just have to live with it, dude.