Game doesn't crash, but goes dark

[Froggy]

I have a unique problem that troubleshooting guides have not covered (as far as I can tell). I purchased the game a few days ago from Steam's Halloween sale (because I missed the humble bundle).
So, I'm not very far along in the game, I'm in the archives finding Daniel's 3 part letters regarding the excavation in Algeria. As soon as I pick up the 3rd note and black out, the light never comes back again. There's something about reaching towards a shimmering blue light, and then there's just darkness. The ambient sound is still there, but there's no footsteps/lantern/cursor/menu, just darkness. The only thing that pops up willingly is the Esc menu. I've saved and restarted, started from the last save point, fiddled around with the settings, updated my graphics card (which helped greatly, BTW), ran it as an admin, updated BIOS, looked for a patch, nothing. I've been looking on the interweb for days trying to fix this because this game is awesome and it scares the crap out of me.
I'd like to get back to it ASAP, so any insight you can provide would be greatly appreciated.
HALP!