Penumbra: Overture graphical glitches and freezes

[Kedjane]

Hey,
When running Overture it works perfectly until the game actually starts. I can see outside the boat (blue, with the grainy effect on) and the map on the table isn't visible. When I move the camera around the boats wall and the map flickers, but as soon as I keep it still it disappears again.
When I hit escape the entire game freezes and I have to tab and quit it by other means.
Any clue what's going on?

Also I couldn't find any patch to the game anywhere, is there one? I've been able to find the one here in Frictionals support section only the link is busted and redirects you to an old 404 message.

Finally got the mood up for playing this again and had a free day... and then this. Discouraging. I hope someone can help quickly. I'm running 1680x1050 (though have tried running the game both in 1024x768 and 1680x1050 by editing the settings file) on XP by the way and tried removing the settings.cfg, the cache and reinstalling the entire game.

EDIT: Oh! I might add that the same thing happens and have been happening for a long time in the 2006 Tech Demo, I didn't realize the two might be related. In the tech demo the floors and walls flicker already in the first room making it near unplayable. When I hit escape the game also freezes. I have been having this problem for year (or even longer) and I figured it was because my computer was too high-tech or something.
Black Plague probably runs well though, played it just a few months ago.

EDIT2: I tried playing some more. Other things that flicker are the rope on the wall, the padlock, the jacket and some other things. The flashlight looked pretty strange before I picked it up. I tried playing beyond that and it seems to work fine once you're off the boat. Black Plague runs great.
So is there any known solution to this Overture/Tech Demo problem, or is it just my computer that's too new? I can handle both Crysis/Crysis Warhead fine on very high/high and I've experienced old games breaking when you get a new computer before.

EDIT3: The problem remains. The ladder down into the first spider tunnels flickers. Same with the pipes and the fence down there. When I hit escape the game froze again and crashed.