Ok, this is an issue that has been giving me an immense amount of
trouble, I'll try to explain it the best I can...I was given a
set of topographic data comprised of polylines, the size and complexity
of the file was such that it is impossible for me to import it into
Revit and be able to edit (grade) the surface once I created a
toposurface. So... the solution I came up with that by all means
should work was to make all the necessary grading changes in AutoCad
before importing the file into Revit and creating the toposurface. This
way once the toposurface is generated in Revit it will already have all
of the grading and places for the building pads in place and all I would
have to do is drop my buildings on top of it. This is where I
cannot figure out what is going wrong...I make the necessary grading
changes in AutoCad and everything looks fine...but once I import the
file into Revit and create the toposurface it gets all messed up...To
illustrate this I will include screen shots of both the AutoCad file
and the Revit file.AutoCad image: http://www.freeimagehosting.net/image.php?8768acfaf3.jpgRevit image:http://www.freeimagehosting.net/image.php?8b5d5f0e96.jpgAny help or suggestions on how to solve this
issue would be greatly appriciated!

From the screenshots it looks like the Autocad data is merely polylines with elevation, not a defined "surface". I assume Revit tries to make a surface from this info and doesn't know how to interpret the abrupt contour changes around the cutout area.Don't know ow to fix it but can guess--create as surface from the polylines first, using something like "edgesurf"-or, do all your grading in Revit. Reduce the file size first by weeding" the contours (lisp routine)