If you're getting this error check the following:
-zoom extents, delete any extraneous points or objects. Do this in plan and elevation views. Objects in the Z plane which are 2 miles away can also cause problems.
-confirm what the units are (we will need this when importing into Revit)
-make sure the that the entire drawing is not too far from the origin-0,0,0. You can move the drawing to 0,0,0 if needed with the move command.
Before you import make sure that you choose the correct import units.
As a side note. When importing site plans it may be a good idea to import the contours separate from the site plan lines. This is because the contours are usually at a proper sea elevation and site elevation while the the other site lines are at 0. You can isolate the contours layer and wblock it.
Here's some additional info and links on Steve Stafford's blog...