Just FYI - after reading this thread I tried using the change device wizard. No luck. The device comes up as online - even tests positive when you do a test run. Later when the scheduled job goes to run - it's offline again. I set up 5 jobs, one for each day. Did successful test runs on all of them. Monday Ran, Tuesday Ran, Wed, Thurs, Fri failed, Monday ran again. There is no pattern to what are called "offline" or not -and test runs fail to identify which ones will later be brought offline. You can right click, successfully bring a particular B2D online, and it will go offline again later when the backup runs.
I have a C: and D: drive that are hard disks. The backup goes to a firewire attached "H" drive that is a Maxtor One Touch. The One-Touch is never taken offline and is constantly available. I was rotating drives, but now I have a fixed drive, that is always connected and two drives that I copy all the files from the fixed drive to so that I can take them offsite. These other two drives rotate daily on and offsite. I did this to avoid having to mount and unmount the target backup drive - but the problem still exists.