Could you try to delete this file manually.
#/etc/init.d/dmgtd stop
Delete /product/CSCO/CW2Kbackup//backup.LOCK
#/etc/init.d/dmgtd start
Delete the dbbackup.log and start with a clean log file.
After it completes then do a Manual backup and wait for it to complete. If you get the error, wait for a few minutes to see if there is a backup already running.