CCL:G: error with Nwchem

From: "clara song" <clarasong83%a%gmail.com>
Subject: CCL:G: error with Nwchem
Date: Thu, 20 Aug 2009 16:21:36 -0400
 Sent to CCL by: "clara  song" [clarasong83*gmail.com]
 Hi,
 I am using Nwchem to do MP2 optimization for Nb_4 anion. The initial structure
 is the optimized one from Gaussian 03, and I think it is a reasonable one.
 However, I got the error meassge:
  driver: task_gradient failed        0
  ------------------------------------------------------------------------
  ------------------------------------------------------------------------
   current input line :
     27: task dft optimize
  ------------------------------------------------------------------------
  ------------------------------------------------------------------------
  There is an error related to the specified geometry
  -----------------------------------------------------------------------
 My input is the following, could anyone plz help me. Many thanks in advance.
 start nb4_tddft
 charge -1
 geometry
 Nb        -0.000012      1.248388     -0.943921
 Nb         0.000012     -1.248506     -0.944053
 Nb         1.247704      0.000044      0.943949
 Nb        -1.247705      0.000073      0.944026
 end
 basis
  Nb library  lanl2dz_ecp
 end
 ecp
  Nb library  lanl2dz_ecp
 end
 DFT
   xc pbe0
   mult 2
 end
 title "UHF optimize"
 task dft optimize
 title "mp2 optimize"
 task mp2 optimize
 title"tddft"
 TDDFT
 NROOTS 3
 TARGET 1
 END
 TASK TDDFT OPTIMIZE