Solved!
You have you're HL video properties set to Software mode! Yes? Yes?
I've been running frantically around a tastefully constructed lab, trying to find the problem in OpenGl! (Which I think worked very nicely in this case)
I'm afraid that your map has too many textures for poor software mode to juggle all at once, which is why some things appear? well, actually, they don?t appear, or even get rendered.
I suggest you either just not use Software mode (which, to those who don?t have an alternative is also rater brutal)
Or do some brutal simplifications ie economizing on textures by stretching them instead of having then tiled, using fewer surfaces, removing those nice looking indentations from around the room. It's there all in Andy's fantastically large r_speeds tutorial. You may find it VERY helpful considering the detail of your map.
I hope I nailed the right problem there. If you can run the map with OpenGl, do and see if it looks any better. If not, then I've found you another problem to worry about.