blanksate is on to something there. Also, did you setup 2nd channel UVs for light mapping? Check smoothing groups as well. Your problem is very common. Sometimes, modular pieces need to be bigger, and sometimes using Unreal's CSG Brushes is the way to go.
Yup, you did the 'move the vertex normals' thing right--well, right enough for the verts that matter for this particular lighting seam at least. (I didn't realize your meshes had depth). But it was like I feared--I seem to remember discovering at one point that UDK did some funky odd stuff on import--like regenerate its…
Try going into the 3d mesh and pushing all the vertex 'normals' UP, solid 90 degrees, perpendicular to the flatplane, so they all face the same way. Maya can do some weird things during creation where it pushes the vert normals outward in a radiating pattern. You want them all standing up like table legs on an upside down…
Creating a 2nd UV channel for lightmaps. I work in max. My knowledge of maya is limited. However, I recently was helping an intern with a UDK personal project he'd created in maya and figured out how to setup the 2nd UV channel for lightmaps. If I can just look at a tool and figure it out, I'm sure you can take the time to…