LOD terrain
 

When I make the terrain in radiant it appears all fine, for example I made a hill and it wasnt to steep or anything when I made it... When I compiled the map and played it, there were these weird humps where my hill was supposed to be. When I walk into the humps I go through the ground.
WHAT THE #5*@ IS GOING ON???????

Hills
 

When you made the map, did you notice if there was any over lapping points? And it shouldn't matter, but did you make it detail or structural?
I've never had any problems with LOD - but just make sure that they aren't that big, and you should be ok...

k thx

The problem here, I think, is that you don't have your LOD set to 100% triangles in Radiant.
If you don't have it set this way, your terrain is not where it appears in Radiant.

To check, in the toolbar go to LOD Terrain, and look where the check mark is in the dropdown window. If it is not by 1 (100%) triangles, then click there to set it that way.
Now when you make your terrain in Radiant, that is exactly where it shows up in your map.