Ok, I'm not exatly new, but it has been a long time since I mapped and I have run into some difficulty...
My problem is, that after I have made a map and compiled it, I try to run it and it loads ok, but then when I spawn in it, I fall right through the grass and keep on flling forever and ever, I have tried several thing but nothing works. I am running it in breakthrough but compiling as a spearhead or AA map does not change the problem...
Move your spawn spots to new locations and make sure they are at least 4 units above the ground. It could also be the texture you choose for the grass.