Situation:
After you install Norton AntiVirus (NAV), you notice that none of the tasks in Microsoft Task Scheduler, including Automatic LiveUpdate, are running as expected. You examined the Scheduled Tasks and notice that all of your tasks, including Symantec NetDetect, show a status of “Could not start.”

The rest of the article gives you a how to fix your configuration. Check it for details.

I ended up using scenario 2 with limited success. It appears to reschedule itself to run in 4 hours if it was successful. If it fails it leaves a message of “Could not start” in the Scheduler. Logging off and back on appears to fix the problem.