When I try creating a scheduled backup with BackupBuddy, I get these errors:
Error scheduling: Error scheduling event with WordPress...Error #3488439b.
Error #874784. WordPress scheduled cron event not found...This may be caused by a conflicting plugin deleting the schedule or manual deletion.
The BackupBuddy Error Codes page says,
This means the built-in WordPress function wp_schedule_event() is returning false. The only thing that can cause that is another plugin or something filtering/blocking scheduling of events. So can try deactivating/disabling all other plugins and then see if it clears it up. If it does then one of them was conflicting and can reactivate the plugins one at a time to find which one causes it again.
I found that deactivating WordPress Text Message solved the problem. When I reactivated, the problem returned.