bicounet on "backup: WP cron does not launch"

Hello,
Avada theme 3.2.1
I encounter a problem with backWPup on a 1and1 hosting (Basic Pack), one of you has he ever met this?
The backup is completed successfully manual to Dropbox (70s).
But automatic backup, the WP cron does not launch.
It remains frozen on "Next execution on 12/02/2013 0:30 by WP-Cron" for today 12/03/2013!
I do not think it comes from the plugin, because with another, same problem.
What might be the problem?
Thank you for your help.