FWIW, I have run into issues with PB's Sprite3D on my test system with a Savage card. Although Sprite3D uses D3D7 and doesn't work, B3D and DBC both of which use D3D7 work fine on that card.
One alternative would be to use PB 4.0 and use the OpenGL subsystem. I know it is not complete and fully implemented, but I do believe right now it will work for Sprite3D.
Personally, I do alphablending and such using the special fx commands and avoid Sprite3D for this very reason.