Black 32-bit textures

We've been consistently getting this problem when placing models with 32-bit RGBA textures in the engine. They show up as black in the shape of the alpha, with no color info and they don't appear to be receiving any lighting.

What's the proper way to get around this issue? We've also tried converting the PNG textures to DXT5 DDS, and instead of displaying the alpha, the entire polygons the texture is assigned goes completely black.

Thanks for the help!