flexbackup could not work
 

Hi all. My flexbackup software in my red hat system has been working fine until recently when i check my log file and found the error stated below:
Trying "mt defblksize" instead of "mt setblk"
Error setting block size
Neither of these commands worked:
mt -f /dev/tape setblk 0
mt -f /dev/tape defblksize 0
I am new to linux and the backup configuration was configured by a previous colleague. How can i solve this?
Thks in advance.