I think it wasn0t the 256 flag, but the mix of multiply blending and alpha blending. Some cards can't take it.
But if a mesh disappears if you reduce the alpha, sounds more like a driver bug to me. I had something similar, then I updated the driver (catalyst) and the problem was solved.
Also, you may swap the texture index for your mutlitexturing, so use an other layer for the alpha texture.
Unfortunatly this isn't really exact science since even the cards interprets these things individually.
BTW yes, you normally need to set the Alpha Bytes "manually", but there's a trick that may speed things up:
Keep a texture in memory that is black and fully transparent. Now use copyrect to copy from this texture to the texture you want to work with. Now draw to the edited texure (eg. Line, Plot or Text). You'll see, the texture is masked.
But if a mesh disappears if you reduce the alpha, sounds more like a driver bug to me. I had something similar, then I updated the driver (catalyst) and the problem was solved.
Also, you may swap the texture index for your mutlitexturing, so use an other layer for the alpha texture.
Unfortunatly this isn't really exact science since even the cards interprets these things individually.
BTW yes, you normally need to set the Alpha Bytes "manually", but there's a trick that may speed things up:
Keep a texture in memory that is black and fully transparent. Now use copyrect to copy from this texture to the texture you want to work with. Now draw to the edited texure (eg. Line, Plot or Text). You'll see, the texture is masked.