I keep dying at random points, although last few times have been at NE Airfield in the prison buildings and usually whilst upstairs. Game says "I think my leg is broken" and the black screen with "you are dead" appears.
Having pressed esc the last time this happened (2 minutes ago), i noticed in the background behind the menu that i could see what looked like the building but very dark and it appeared that i had clipped through the floor.