I would try increasing your tension.
If tension is too low the results can be
outrageous.
We generated a DEM with a tension of 60.
Keith M. Mitchell
University of Illinois
Department of Agronomy
S-316 Turner Hall
1102 S. Goodwin Ave.
Urbana, Il. 61801
(217) 333-9648
keith@piked2.agn.uiuc.edu