I'm betting his problem is the lack of info_player_survivor or info_player_zombie entities, so as a result he's spawning at the origin of the map. And he didn't put any map stuff at the origin, so the character falls.
Your problem might be the lack of cubemaps
. Add some env_cubemaps to the center of every room and every large area, compile, then run the map and type 'buildcubemaps' without quotes. Then restart the map.
If that doesn't fix it, then you might be using the d.e.a.d textures. Avoid those, lots of them are buggy and incomplete.
PS - Also, bit of a bump on this thread, isn't it?