problem with light

HI
i have 2 desert model in a map and both of them has terrain shader in shade-c with same properties .my problem is : one of them is brighter tan other.
why?
can any one help me?

any idea?
is it for sun?
all properties like shader are the same.
is there any to solve this problem?

I don't know the shader and thus I don't no if it uses the terrain's ambient, but try setting its UNLIT flag (either in WED or at the beginning of its action).