This is the line that will combine diffuse color, night lights and specular reflection. vEff.rgb is the night light color and the intensity is controlled by aux.a (aux.w). So, it looks like something is mixing up the vector components in your computer. (vEff.a is the specular water/land mask)
A vector component like aux.a (or aux.w) can be also addressed as frg.aux[3]. The index is from range 0 to 3. You could change all frg.aux.* to use the format frg.aux
[*] from the PlanetTechPS section.
I have seen the tiling effect a few times after installing a broken add-on. The texture file is probably corrupt. Does it occur in a clean installation.
Of course, all these anomalies could be caused by the same problem with the effect compiler or with the GPU.
Thanks. It still happens with a clean Orbiter installation. I tried the frg.aux
[*] solution and the nightlights came back. When I entered the line frg.aux[1]=0, which I suppose is equivalent to the earlier fix (frg.aux.b=0), it removed them again. It seems this is going to be the only workaround for my not too good integrated graphics chip.
Thanks for your help.