Frustrating textureing problem with FSDS.

Hi to all. I have a frustrating textureing problem with FSDS.I am making a hangar using a five sided tube with ends closed.I form the desired shape and texture it using the poly method.and make sure the night texture box is ticked.All textures show OK but the night textures only show on one side of the hangar when viewed in FS. Has anyone seen this before?If I use a "cube" for the body of the hangar and a three sided "tube" for the roof all textures, day and night ,show on the " cube" but the LM texture shows only on one side of the roof. Seem some sort of problem with the "tube" structure.Any thoughts out there? Thanks in Advance,Aussie.