My computer does this too, an I've tested some self-created meshes, one of which has the same transparency problem:
It seems that it ONLY affects objects shaped like spheres! I thought it was caused by the haze around the planet, and it might be related...
I tried a Dyson Sphere (36,000) units radius, with both an inside and an outside, and both surfaces had the transparency issue... The Dyson Sphere replaced an ICE planet, and the radius of the haze was only 5000, so the haze might not be it...
...also tried a Planet-Remnant, and it worked fine (which is consistent with the pirate base being displayed normally, and the remnant had RenderAsVolcanic...
*************
I'll try isolating which combination of things causes it...
I'll also try slightly corrupting a perfect sphere mesh to see at what point the problem decides to kick-in
The solution MAY be to render everything as volcanic, and I'll test that too...
*********
Oh, and I think I don't have a video card at all, just software... ...The side panel is off, so I can just peek in when I go to that computer... (I think I just have chip-memory, with no proper card)
Also, I believe the textures do load, as I can make it so they are only transparent on the dark side of the mesh (why aren't there all three texture maps for a planet, in it's mesh file?)