That's indeed strange, here's a link to a small demo of the fog, maybe it can help you

http://m_auer.byethost3.com/3dgs/fog/fog.html
(you just have to click on download at this site)

maybe you should try to add the "fog_color = 1;" at the end of your main file - because as far as i have seen you use templates which could set the fog for themselves.