I don't think you're necessarily interpreting the log right. The Migration Assistant messes up a file on your drive that controls ownership. We fix that, and then (in the log) indicate you should restart your Mac to have the fix take full effect... running again will work in some cases, as it did in yours.

I want to second Chris_Porter's problem/confusion.
I too had no idea that 1-minute-ahead-of-backup was the required time for wakeup. I too reasoned that, say, using Energy Saver to wake up the computer 10 minutes before backup would be fine if the computer was also set to go to sleep only after 20min of inactivity. And I too am finding that my scheduled backups don't always happen.

In fact, sometimes the backup that should have happened at 2am instead begins when I wake up the computer when I get up in the morning at, say, 9am.

I can try setting wakeup for just 1 minute before backup, but this is an inadequate solution because I actually have 2 other quick routines that I want to have run before SD does its full backup (MailSteward and an applescript I wrote to make versioned copies of iCal and AddressBook databases).

There's really not much I can do about the fact that the OS puts the Mac to sleep quickly, UniAce... if we can't even get started before it goes to sleep, there's no way for us to keep it awake.

I know it's not your fauly; I understand.
I wish this general issue of scheduled wakeups and subsequent sleep was more widely known. There must be other contexts in which users are affected by this. I wonder if anyone elsewhere was made progress in udnerstanding why it happens or what might be done about it.