I had an issue where if you have an account running under ‘domainName\Username’ and changed something to an existing task, the Task Scheduler would throw up the error ‘One or more of the specified arguments are not valid’. This was particularly annoying because you could spend 10 minutes trying to find out what you did wrong.
1a. The fix is to open the properties, go to the user it is running as, and point to the user in the directory again. In my case with went from ‘gerry’ to ‘testlab.test\gerry’ and it worked. It’s like it needs to refresh the user who is running the task to have the ‘domainName\UserName’ format.