This error message occurs when the MDP service does not have sufficient rights to edit the schedule, maybe there has been a change of credentials either on the MDP end, or the account under which the task scheduler service runs.
I am going through datapump clearing out jobs that are no longer in use and such. I got two jobs that when I try to delete them it gives me the error message 'Error while testing whether schedule exists'. The process still runs daily but you can't even get in it to edit the schedule.(gives you the same error message)
Also we changed the name convention of all our processes. I noticed that when I changed the process name. The schedule changed too, so I had to reset that. I there an easy way to remove all of the scheduled tasks that aren't really scheduled? /b[/quote]