Are you sure you're using the right modter bricks? The default ones are called Brick_ModTer_BasicPack and Brick_ModTer_InvertedPack. Make sure there are no folders with the same name.
Also, make sure that the files are not read-only and your add-ons folder is not read-only.
I'll give it a look when I'm finished with my work.
This is cool, could you put up a download? I want to build some stuff in that cool terrain! If I do build something and if I even post a gallery thread credit will be awarded. It would be awesome if this started a new type of thread where it is just blank terrain that you can fill yourself.
Hah, it would be very helpful for people who are still terrain wanting, they can just download premade maps instead. It's kind of like bringing back the maps and stuff.
EDIT: I found out that the mod Build Zones, the one that gives you a zone to build in and you can not build outside that zone, forgeted up the build. I'm curious to why it didn't effect modular bricks, but normal bricks it did, even when disabled. Rest assured I disabled it and it's all working now, which allows me to continue the edits and build more.
I'll just leave this here then.

Haha yes, that. I built most of that terrain for you anyways Alk, you should have seen it coming that I would spew out more terrains.
SECOND EDITAdded ramps to the side of the map so you can get up and down the canyon side.

