Framerate issues with Amnesia: The Dark Descent

[AdamAK]

EDIT: Terribly sorry! I accidentally posted the thread in the Penumbra forum, rather than the Amnesia forum. Could a kind moderator please move it to the correct section?
Hello everyone,

It's been many months now since I have bought Amnesia, and I've had dozens of hours of fun with it. A few months ago, however, the game started running terribly. Regardless of what settings I use the framerate is dreadful, and the game is practically unplayable. I have not made any adjustments to my computer over the past few months, and this issue arose quite suddenly. I have tried things like updating my GPU drivers, and have even rolled back to the original ones now as well, but nothing seems to make a difference. No important software or hardware changes have been made since I've been playing Amnesia; just a few games being installed and such.

The odd thing is thus that I used to be able to play this game on high settings while streaming it while getting a solid 40/50+ fps, and now I'm getting sub 15 fps on the lowest settings without even streaming it.

Any ideas on what could be causing it?

I'm attaching a dxdiag file, but in short, my specs are:
i7-2630QM
4GB DDR3 RAM
Nvidia GeForce GT540M

EDIT2: Added the hpl.log file.

[Acies]

Just a guess:
Have you recently cleaned your fans? Summer has arrived and things are getting warmer. Having dust in your fans might increase CPU temperatures to levels which creates lag in games (at least for me).

[AdamAK]

Summer hasn't really arrived in my country, sadly. Besides, this issue started in early March (quite suddenly), when it was still pretty chilly out here. My idle CPU temperatures are sitting at a regular level.
Furthermore, my other games run fine on this laptop and only Amnesia is giving me trouble.

I'll clean my fans again, but I'm quite sure the problem I'm having is not really hardware-based.

[plutomaniac]

from where did you get the game?

[AdamAK]

I bought it on Steam back in August 2011.

[plutomaniac]

do a file integrity check

[AdamAK]

I did a file integrity check, but the game has been re-installed several times over the past few months anyway (during my attempts to fix the problem).

I've managed to make the game playable (the low fps kicks in later, and is mainly an issue in larger rooms) while streaming, but it's still underperforming substantially compared to how it used to run.

[plutomaniac]

maybe you have programs that interfere installed

[AdamAK]

Doesn't look like it. I've tried disabling background programs, but it didn't make any noticeable difference.

I've also run several malware sweeps, but they didn't find anything, so it's not a virus either (though that would've clearly affected all my games, rather than just Amnesia).

[plutomaniac]

after doing another file integrity check, run the game until it starts to lag and reattach the hpl.log file