SD! mounts disk but doesn't unmount
 

2.6.4 (v89)
In the past, SD! used to unmount the disk, but now doesn't. I wake up the MacBook for the backup with a schedule in system prefs. The disk is still mounted in the morning.
I'd like to minimize the time that the Lacie drive is spinning, so would like to get it to unmount so that it will spin down.

advice?

MacBook Pro
10.6.8
Lacie d2 quadra 500 GB

Delete and recreate the schedule. Let's see if that helps.