im now getting this error 
ERROR: MAX_MAP_TRIANGLES (3072000) exceeded
The error is pretty straight forward, you have too much triangles in your map, the maximum I would recommend would be something around 2000000 tris for a good computer in a modern engine(certainly not Radiant), try optimizing your map, remove high poly models, reduce patch detail, caulk useless brush faces.
Lol but getting this error really means you did something very bad.
Inside Radiant there is a debug view named Try Densit, use it to keep track of wich place have too many polygons.