Okay, my graphics driver is completely up to date, the shader is set to very low, and now the psychedelic's gone, and I seem to be able to see all the models i'm supposed to.
Now other glitches have come up
It's incredibly bright, and I don't know how to change it. There's no difference at all whether or not I have my flashlight or glowstick out. I encountered a similar problem when I played Oblivion, in that everything seemed much better lit than it should have been.
I haven't gotten very far, so I can't say for sure if the old glitches are gone for good, but at least it's playable. Still bummed out about the brightness, it really takes from the tension if I can see perfectly well in an abandoned mine hundreds of feet below the surface.