Scheduled backups have failed consistently since 1 June 2012, ie immediately after the upgrade to 4.1.3.
I have four scheduled (incremental) backups that all show their correct timing - none has run since 1 June. There are no no logs created and therefore no errors to report. Manually running the backups creates valid backup files.
Comodo Backup 4.1.3
Avast! AV 7.0.1426
Update to the issue - when exploring the saved schedules the folders selected for backup have duplicated themselves so that I have two identical instances to backup at the same time - this appears to be the problem. Editing the saved schedules to show just one instance of the folders to save appears to solve the problem.