Mystery Solved! After looking in the "Task" folder and reviewing the "Resident Protection" Task, I discovered the "Default" setting had been inadvertently turned off. So it was easily resolved, and upon restarting the computer, and checking Control Panel "Security" I was able to confirm the avast! antivirus was initiating properly and running continuously. So, anyone setting up tasks (scan criteria or scheduling scans) should make sure the "Resident Protection" default setting does not get turned off, which would leave your PC unprotected.