Whenever I add a sky box to contain my level and try to build the map, it tells me that "block 0 is concave". Levels that other people have made do not have this problem, just levels that I make.

I am using A7 if it matters.

Also, without the box the map compiler tells me the level is leaking. Is this because I do not have a sky box?

Last night as I was playing around with WED, I found that as long as I don't give the box a sky texture, it compiles fine. It only warns me that the level is leaking.

I think I found the solution: set the mesh size to zero, then check the "create meshes button" in the map compiler.