Terrain too complex for interpolator

[Madz]

Hi All

I'm using Home Designer Pro 2012 and have run into this error a couple of times now:

"The terrain interpolator is ignoring terrain breaks and retaining walls due to complexity of the calculation"

Last time I was able to jiggle the retaining walls around and get it working again without really understanding what the issue was, but this time I'm stuck. Is there some sort of complexity threshold I might legitimately be hitting or most likely a sign something is incorrect in my plan? I'm modelling about 7 acres of sloping terrain and have various contour lines, terrain areas, retaining walls and some actual measured elevation points in there - so there's a bit of work for the terrain generator to do. It's the first time I've seriously tried to use terrains though so I have no feel for the limitations or power of this feature. Maybe that should be a walk in the park for it!

Searching on the error message comes up blank - have others encountered it? Is there something that is commonly causing the problem - unfortunately the message doesn't much indication where to look for the issue - I changed a few elevations and retaining walls before trying to regenerate and now I can't seem to get it back to working.

Very frustrated as I'm in the final stages or preparing our council plans and for the most part Home Designer has served me really well, I'm very happy with what I've been able to produce with it. Any help to solve this one would be greatly appreciated.

Thanks
Mick