Norton antivirus task scheduler error in Vista

I have Norton Antivirus recent edition 16.7.2.11 (2009), and the both my settings in Norton and my settings in the Task scheduler show that I have a full scan scheduled daily, but it will not run. What does run is an idle quick scan, which I clearly switch to "don't run" on my Norton settings. Each days attempt to perform a full scan has failed. I have no problems with updates. History shows launch and run failure event codes 103 and 203. Any ideas. I know the task scheduler works, I also run Webroot Spy sweeper without scheduling problems at all, as well as Google updates.