I'm getting the same luminosity - or lack of - on the 6800GS and the 5900XT, could be something with nVidia hardware/drivers, I can give it a try on the x600-based laptop later today.

Also on the AXP2200+ machine (512MB ram, with a 5900XT with 128 MB), I've had the game startup take 40-50 seconds on first execution (subsequent executions were faster) as it had to swap out other proggies from the memory: during load time, the game requests more than 300 MB (not sure of the exact figure, but there is a definite spike in the taskmanager). When running, it uses about 120 MB, which is reasonnable.
The 'texturem.jpg' is probably the one to watch, it should be about 50 MB when decompressed, chances are you have quite a few copies of it in memory at some point. I resampled it to 1024x1024 and the game loaded and started instantaneously (and framerate didn't change that much), so it's definetely seems to be something that happens at load time, as the hardware can handle the high-res texture fine at render-time.