Saint, for one thing that ediotr is VERY flakey, I have found that what ya ned to do is..
after yer done doing everything close the right side it will ask you to save, say yes.
then exit out totally and come back in. everything will be the same as before.
the hit set terrain and name it (sometimes the name will not be the one you picked though ??)
then click BUILD
most of the time my stuff has ended out all flat it was because i forgot to save it before i clicked build, so the last save (before i did hills and stuff) was used to build the map
I wish the editor was better, even if you do everything right it still might eat yer map.