Backup fails first time with (21,8) error on UserId

I am trying the Demo version that I downloaded a couple days ago, and hoping this works well so I can buy it when the Demo is up. I tried to set up the Backup process, but when the first backup tried to run I received an error (21,8) on some UserId:

Thanks for the help!

On a side note, the login box never came up on Firefox - it was a small white box with no data fields in it. I had to go to a different browser to do this.

Does anyone have any ideas about this?

Hello Don,
seems like this Task Scheduler stopped the backup from running.
Check the Microsoft Windows Task Scheduler and see if the eM Client backup task is set to ‘Run only when user is logged on’.
Then either change this option to ‘Run whether user is logged on or not’ or click “Change user” and select yourself again, as there could be an issue with your User SID recognition.