After 4 Tier 2 support sessions the problem is gone. Tech support deinstalled MOBK and deletet registry entries. Later a new version of MOBK could be installed. But it couldnot be reached from Security Center any longer, the entry for Online-Backup was no longer
I made the decision to deinstal McAfee completely using the removal tool and installed it again. The MOBK tool is now the old version and everythink is working fine. No attempts to update after executing the backup. No file under programdata trying to update it any longer.