Here is my two cents worth (for what it's worth). I have seen this in cod2 when I clipped a brush. Sometimes it happened to me when I clipped a brush that had been rotated. You could shoot at it and it would act like concrete but it was like a caulk brush (invisible but solid).
The last brush I saw this on was right on the grid lines (snapped to grid). I clipped both ends, compiled then play tested the map. Both ends that I clipped were not showing the texture (just like I had caulked it instead).
The first time this happened to me I had to rebuild the brush completely. Don't know why this happens. Maybe someone else can figure it out.

The not welding vertices and edges together has an effect on the walls too.

redrum thats exactly what is happening to me, now i re made some fields, changed a road texture next to the field, not touching it and the field ended up having an even bigger hole there

am still having no luck, any 1 got a clue ?

I haven't figured out how to fix that so far. From the pictures you posted up it looks like a sky texture with clouds. Is that what it looks like?
I wonder if there is a way to unweld the terrain patch vertices?

yes you pull the two apart, but i have welded farm pieces together but nothing is welded to the road its just caulk pieces placed next to the road then clipped to the edge of the road, its fustrating, and the sky texture is the skybox

owt new ?

nevermind, i believe the problem was that brushes were overlapping, but the road dissapearence is totally confusing, so i have decided to re build that area.