Deleted, only just realised you were talking about an ancient simulator that nobody uses anymore, joke ;)

Hello!The problem lies in the root of FS9.The world of FS9 is flat and square.But your view is marked around it, to the maximum ofset visibility.The clouds are like ground textures but shown in the square,your visibility is limited in radius.Imagine you are standing in the middle of a square room.The walls are 10 meters away from you.You can because of the visibility restrictions but only see the 10 meters.This shows that you can see the walls only when they are apart of the radius.The corners can not see because they are further away than the closest distanceto the wall. So it is in the clouds, The ones in the corners of the displayare further out than your sight set. Therefore, they are hidden. Expressed hope that's understandable, since this translation has brought me google.

Then why doesn't everyone have this situation?

This is an FS9 problem as the others pointed out, same here.Jan-Paul

And I have never seen it so what is special about my set up I wonder?!

Hello,Whether this feature can be observed is also dependent on the installed textures. When using good textures can be observed that, because the background color of the sky with the clouds should be the same colour. Then comes the error does not occur. To avoid this I like to use textures of Cielosim. Their textures are also able to masterfully blurred the sharp Horiizont.Furthermore, it also depends on how fast your PC is on the representation of the shallow cloud fields (there is no real 3D clouds in a flight simulator) can be rotated. These fields are always turning toward the viewer. When the CPU and GPU so that not even meet, this error can also be seen.And when times turn out a field of maximum visibility, you can see it too. The cloud disappears.Hope you can understand this, its translatet into english by google.Greetings