Sandro - When I'm creating unwrapping for light maps, I usually just use the pixel snap tool in Textools when I'm done. I set the map size to what I plan on using for the lightmap in UDK, and then the pixel snap tool snaps the borders of shells to the nearest pixel. It's more of a workaround than an actual fix, but it…
Those seems may be caused by your light map seams falling in between two different pixels. Since the background of the light map is automatically filled with black, this can cause seams to show up along UV borders. Check out this video for a more in-depth explanation.…