Like you said on Started to not back up weekly I'd installed the WP Control and I can see three process:
dbmanager_cron_backup  2013/10/18 15:10:32 (2 hours 1 minute) 1 day
dbmanager_cron_optimize  2013/10/18 13:07:32 (now) 3 days
dbmanager_cron_repair  2013/10/18 15:09:32 (2 hours) 2 weeks
I'd tried to change the schedule time or run manually, from the plugin, but doesn't work. If I do the manually back up, works fine.
I have installed this plugin on others websites and everything works without any problem.
Thanks a lot for your help.