I bought the full game, but I have one of those issues too. Nothing wrong with the floor, but the shadows flicker like hell everywhere. Many times items get fully covered by blackness and I need to move or turn the mouse a bit, so that I can see them. It gets pretty annoying over time, that's for sure.
Maybe this is due to my graphics card, which is an ATI Radeon 9600. I'm not sure, but since it's the barely supported, it may be. Drivers should be up to date since I switched to this card very recently.
Other than that I only have the game crashing at some point, sometimes, but testing lead me to believe that it's due to some graphics setting that, thus, I should avoid. (This may relate to the card too...)
Anyway, it's not a big issue to me, because I'm going to mount my own pc today, and I'll be playing the game without problems in it (hopefully
) from today onwards, but since I saw the same problem in the full game, not the demo, I thought I'd do good to confirm it.
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AMD Athlon 1.8GHz
1GB dual-channel + 250MB RAM
win7 32bits
ATI Radeon 9600