Building Night Textures

I use FSDS 3.5 to create building models and create daytime textures from photos. Using PaintShop Pro, I use shadow and recoloring to the daytime texture to create a nighttime texture with _lm added to the filename. The nighttime option is checked when importing the textures into FSDS, and a .N is indicated on the texture name within FSDS.I am apparently not doing this right because the nighttime texture does not display in FSX at night. Instead, I get a darkened daytime texture. Can anyone explain to me what is wrong?Thanks.ArtBiostar TF560-A2+ | Athlon 64X2-6000+ | 4GB PC2-6400 RAM | Geforce 8800GTS-320MB | 500W PSU | 250GB HD | FSX(SP1-Acceleration) | UTX | Audigy SE sound | Vista Home Premium 32 bit | CH Yoke (modified) & Pedals | Logitech Extreme 3D Pro Joystick | 22" WS LCD monitor