No ground textures.
I have seen that happen in DL from time to time.
That is also my first indication that I went too far and the game is about to crash with the dreaded Out-of-Memory error.
If I try to save the game after I see this, it will fail and I will be OoM.
But that only happens if I do way too much during a single turn, like say, destroy most or all of the enemies ships then go on to invade 20-30 planets.