Chinchilla Killah

So I'm up to Kva, early part of the demo. I quicksaved and decided to exist after killing a bunch of rats in the south-east "cave"(?) area. When I came back, I got this: The ground appears to be black, and the gameplay is severely lagged - so much that it does not appear to respond to mouse clicks. Keyboard commands still work, albeit with a delayed reaction, and the whole experience is generally unpleasant. Referring to an autosave doesn't appear to fix the problem, nor does reducing the draw graphics system, nor does saving over the quicksave at Avadon and travelling over again. Please fix.