There was a terribly weird bug that made the menu appear pure black after returning to it from the game itself.
Finally it was located being in the drawing code of the ingame hud. The code set a d3d transformation that was based on the resolution of the screen. The transformation wasn't corrected when entering the menu that had different resolution, so the whole thing was drawn offscreen. That's all about it. Nearly two hours wasted.
And a screen of the menu itself: