[d_u]

Вот все и решилось:
I was receiving the infamous ""the selected task "{0}" no longer exists. to see the current task, click refresh..." Using the information in these posts I went to the "Defrag" folder under the Task Scheduler Library/microsoft. When I clicked on the folder, I received the same message. Apparently the task information was missing. I then went into the Windows 7 "Disk Defragmenter" application and configured the schedule again ( Run at 1:00 AM on day 1 of every month). This put the task back into the Defrag folder in Task Scheduler. ...and, no more error message.