Amnesia TDD crashes on startup

[EclecticMonk]

I bought Amnesia: The Dark Descent on Steam for my desktop PC. Specs are as follows:
OS: Windows 7 Home Premium 64-bit
CPU: Intel Core i5-2500K
GPU: AMD Radeon R9 270X 2GB
RAM: 8GB

The launcher starts OK, but when I try to launch the game the launcher closes but the game doesn't start. I've tried deleting my main_settings.cfg and launching the game without changing any settings, disabling my anti-virus and firewall and reinstalling the game. I've also tried starting the launcher as Administrator. Nothing helps. I have the latest driver for my GPU (Catalyst 14.4).

There is no HPL.log file in my Documents/Amnesia/Main folder - only launcher.log, which I've attached.

If I run Task Manager, I can see an Amnesia.exe process starting up, but it terminates after a few seconds. Each time I try to start the game, I get an Application Error and Windows Error Reporting event in my Windows Application log. Looks like an access violation in ntdll.dll:

Fault bucket 3948566213, type 1
Event Name: APPCRASH
Response: Not available
Cab Id: 0

Problem signature:
P1: Amnesia.exe
P2: 0.0.0.0
P3: 4db7bc06
P4: ntdll.dll
P5: 6.1.7601.18247
P6: 521ea8e7
P7: c0000005
P8: 0002e3be
P9:
P10: