When I run the game at a 2560 x 1600 resolution (my monitor's native res), the main menu and everything works just fine at first, but when I start a game the screen is just completely beige with the GUI on top of that.
Screenshot
Furthermore, when I browse through the menus (especially the ones with the 3D units), it runs at around 0.5-1 FPS.
And the textures for one of the default units (the first one) don't load.
Lowering the resolution to, for example, 1680x1050 fixes all this.
Debug.err
DxDiag copy-pasta