Ok, I've found out why 4.01 doesn't work with GP3. When adding support for CSM I made a mistake regarding GP3. If it's GP3 it still assumes it's GP4 and goes ahead with something that always crashes with GP3. As a workaround, you can use 4.00 with GP3, until I release 4.02.
As for GP4 not working, it's still not clear why. It's unrelated to the GP3 problem. Did you also try 4.00 with GP4? The only reason I can see for a premature ending of GP4 is a failed CD check. But it would first show a message in-game about this. Another reason could be a DirectX initialization problem. Did you also try to run GP4 from GPxPatch 4.01 with debug mode off?
@pirx: I'll add this to the todo list.
René Smit, Independent Software Developer.
Download my GPx tools
here.