Need help on extracting DEM data!!

[Subbarao Vedula]

I was trying to read DEM data from 1/2" tape drive into my SUN account using
"m.dem.extract" command. I gave the input file name as  /dev/rmt0 (1600bpi)
and blocksize as 4096. Then its saying
 
"Reading Elevation Tape...     
ERROR: error reading tape".

When I ran "m.dem.examine", it gave the following results:

--------------------------------------------------------------------------------

PHENIX CITY - W                  AL,GA          NI

min elevation: 45.000000  max elevation: 305.000000

ns_res: 0.000000  ew_res: 0.000000
# of columns in file =   809773872

file north UTM = 118800.000000
file south UTM = 115200.000000
file east UTM = 0.000000
file west UTM = -309600.000000
--------------------------------------------------------------------------------

MONTGOMERY - E                   AL             NI

min elevation: 24.000000  max elevation: 383.000000

ns_res: 0.000000  ew_res: 0.000000
# of columns in file =   809773872

file north UTM = 118800.000000
file south UTM = 115200.000000
file east UTM = 0.000000
file west UTM = -313200.000000
--------------------------------------------------------------------------------

MONTGOMERY - W                   AL             NI

min elevation: 9.000000  max elevation: 212.000000

ns_res: 0.000000  ew_res: 0.000000
# of columns in file =   809773872

file north UTM = 118800.000000
file south UTM = 115200.000000
file east UTM = 0.000000
file west UTM = -316800.000000
tape min elevation:9  tape max elevation:383
--------------------------------------------------------------------------------



My current Window Settings-----------------------------
rows:       241
cols:       266
north:      3635500.000000
south:      3575250.000000
east:       688500.000000
west:       622000.000000
ns_res:     250.000000
ew_res:     250.000000


Am I doing something wrong?
Could some one help me out pleaase!!

Subbarao Vedula