Need help on extracting DEM data!!

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