Hi everyone,
You're gonna hate me for this. But, I somehow managed to install it normally on my system running on Win XP Pro and even updated with the 1.2 patch. Then, I started playing and oddly enough, I DID NOT encounter any problems!!!
I even experimented with the Chaos cultist laspistol bug and it was fine. I'm now almost halfway through the campaign (again) and it's all good so far. So, I suspect the problem might be with newer systems and drivers. My PC is a Frankenstein monster of old parts and new. I still use a 32Mb GeForce 2 MX with DirectX 9.
PS. Game setting is at 1024 x 768, same as desktop.