CDO

i'm trying to convert NCEP FNL to netCDF format,
but there is some problem as below:

[yiling@OFSSD 2010Megi]$ cdo -f nc copy *.grb test.nc
cdo copy: Open failed on >fnl_20101001_12_00.grb<
Unsupported file structure

Print my version number. ===========================================================================================
[yiling@OFSSD 2010Megi]$ cdo -V
Climate Data Operators version 1.6.4rc1 (http://code.zmaw.de/projects/cdo)
Compiled: by yiling on OFSSD.csrsr.ncu.edu.tw (x86_64-unknown-linux-gnu) Mar 25 2014 18:07:40
Compiler: gcc -std=gnu99 -g -O2 -pthread
version: gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-54)
Features: PTHREADS SZ Z JASPER PROJ.4
Libraries: proj/4.8
Filetypes: srv ext ieg grb grb2 nc
CDI library version : 1.6.4rc2 of Mar 25 2014 18:07:31
CGRIBEX library version : 1.6.4 of Feb 26 2014 11:29:56
GRIB_API library version : 1.9.16
netCDF library version : 4.2 of Mar 25 2014 18:00:11 $
HDF5 library version : 1.8.8
SERVICE library version : 1.3.1 of Mar 25 2014 18:07:17
EXTRA library version : 1.3.1 of Mar 25 2014 18:07:12
IEG library version : 1.3.1 of Mar 25 2014 18:07:15
FILE library version : 1.8.2 of Mar 25 2014 18:07:13

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Could anybody help and guidance to solve this problem?
Many thanks and Best regards

ohihi