Today I launched SH3 with GWX and my usual mods and... Voilą!!!! Te flat sun is gone!!!
Tried both settings, RickSarg's and Fifi's and with both of them it works fine.... don't know what happened, but we are beck to normal now.
I suspect that in some occasions the SH5 Environment mod causes the flat sun, but I wonder why it does occasionally...
I decided to stop using this mod to avoid further problems.
CapZap