Tape read error

[student]

Hi,
 I have been using  hp surestore dat 24 External tape drive with a hp
dd3 data cartridge for backing up /var filesystem. I am using FreeBSD
4.9.

I can do the back up using the dump command. However when I try to
restore the filesystem , I get an error
taperead error : Input/output error.

 I have gone into /var directory and typed the interactive command.

# restore -i -f /dev/nrsa0

I also tried the command

# restore r

Bothe of them give me an error.

Can somebody help me?

Verghese George