GU: Choosing simetry group

[dasf@beta.df.ufpe.br (Demetrio A. Da Silva Filho)]

Dear friends,

I was studing group theory and I learned that I can improve my calculations
using the simetry of the molecula. I have a poliacetilene with a soliton and
as we know it have simetry of reflection. So, I can use the group C2v, right?
I tried to change the simetry in the input that I already runned using C1 simetry group but I got this answer:

 THE POINT GROUP OF THE MOLECULE IS CNV
 THE ORDER OF THE PRINCIPAL AXIS IS     2
 **** ERROR READING VARIABLE X0       CHECK COLUMN  2
  c            6    0.000000            0.000000            0.000000
 
 
 
 ....V....1....V....2....V....3....V....4....V....5....V....6....V....7....V....
8

what is wrong? 
Thanks in Advance
Demetrio FIlho
dasf@df.ufpe.br