This error occurs because the scheduled Standardization jobs are owned by the inactive user referenced in the error message.  Here are the steps to verify that this is the case:
  1. Navigate to Setup > Administration Setup > Monitoring > click Scheduled Jobs.
  2. Check for jobs that list the inactive user in the Submitted By column. 
  3. The jobs that impact the Standardization are AccountStandardization and/or ContactStandardization.
Once you've identified which jobs need to be updated, follow these steps to transfer them to another user:
  1. The ContactStandardization and AccountStandardization are disabled on the Utilities tab.
  2. Disable the jobs and make sure there are no active instances of them currently running. 
  3. Log in (if not already) as the user that you want to own the jobs.
  4. Go to the Utilities tab and enable the jobs. The scheduled jobs should now owned by the new user.
  5. Verify the job ownership by viewing the Scheduled Jobs list.
In order to avoid additional errors when standardizing or merging Contacts, it is best to mass transfer ownership of Accounts and Contacts from the inactive user to an active user.